Flexible microwave catheters for natural or artificial lumens

ABSTRACT

A method for forming a resonating structure within a body lumen, the method including advancing a flexible microwave catheter into a body lumen of a patient, the flexible microwave catheter including a radiating portion at the distal end of the flexible microwave catheter, the radiating portion configured to receive microwave energy, and at least one centering device proximate the radiating portion configured to deploy radially outward from the flexible microwave catheter; positioning the radiating portion near tissue of interest; deploying the at least one centering device radially outward from the flexible microwave catheter within the body lumen such that a longitudinal axis of the radiating portion is substantially parallel with and at a fixed distance from a longitudinal axis of the body lumen near the targeted tissue; and delivering microwave energy to the radiating portion such that a circumferentially balanced resonating structure is formed with the body lumen.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/524,674, filed on Jul. 29, 2019, now U.S. Pat. No. 11,234,765, whichis a continuation of U.S. application Ser. No. 13/442,831, filed on Apr.9, 2012, now U.S. Pat. No. 10,363,094, which claims the benefit of thefiling date of provisional U.S. Patent Application No. 61/473,564, filedon Apr. 8, 2011, the entire contents of each of which are incorporatedherein by reference.

FIELD

The present disclosure relates generally to flexible microwave cathetersfor natural or artificial lumens, and related methods of assembly anduse.

BACKGROUND

Energy-based tissue treatment is known in the art. Various types ofenergy (e.g., electrical, ultrasonic, microwave, cryogenic, thermal,laser, and so forth) are applied to tissue to achieve a desired result.Disclosed are microwave catheters that enable microwave energy to beeffectively delivered within a natural lumen within a body, to alocation accessible through a natural or artificial lumen within a body,and/or a body structure such as, for example, an internal organ or bodystructure.

One such family of natural lumens includes lumens related to thegastrointestinal system (e.g., mouth, pharynx, esophagus, stomach,pancreatic structures, small and large bowel, bile duct, rectum andanus). Another such family of natural lumens includes lumens related tothe auditory system (e.g., auditory canal and Eustachian tube). Yetanother such family of natural lumens includes lumens related to therespiratory system (e.g., nasal vestibules, nasal cavity, sinus, tracheaand the main and lobar bronchus). Another such family of natural lumensincludes lumens related to the urinary system (e.g., urethra, bladder,ureter, prostate, and kidney). Another such family of natural lumensincludes lumens related to the female reproductive system (e.g., vagina,cervix, uterus, fallopian tubes, and ovaries). Another such family ofnatural lumens includes lumens related to the male reproductive system(e.g., urethra, ejaculatory duct, vas deferens, and testis). Othernatural lumens may require access via other means, such as commonintravascular procedures to gain access to the lumens associated withthe vascular system (aorta, arteries, veins, chambers of the heart).Additionally, the lumens associated with the vascular system may providea pathway and/or access to all internal organs/body structures (e.g.,access to the heart, lungs, kidneys, liver, stomach, intestine, colon,spleen, gall bladder and appendix).

It is believed that renal sympathetic nerve activity initiates, andsustains, the elevation of blood pressure. Chronic elevated bloodpressure, or hypertension, is a significant cause of heart disease anddeath and afflicts millions worldwide. Generally, one having chronicblood pressure of over 140 mm Hg systolic and 90 mm Hg diastolic isclassified as suffering from hypertension. Renal denervation has beenfound to reduce blood pressure. The renal nerves are bundled around therenal artery, which is readily accessible via the femoral artery.Targeting the renal nerves result in additional beneficial outcomesbeyond blood pressure reduction which may become primary motivations forthe procedure such as metabolic syndrome, heart failure, sleep apneasyndrome, renal insufficiency and diabetic nephropathy

SUMMARY

In an aspect of the present disclosure, a flexible microwave catheter isprovided. The disclosed flexible microwave catheter includes a flexiblecoaxial cable having an inner conductor, an inner dielectric coaxiallydisposed about the inner conductor, and an outer conductor coaxiallydisposed about the inner dielectric. The disclosed flexible microwavecatheter includes at least one feedpoint defining a microwave radiatingportion of the flexible coaxial cable. A mesh structure having acollapsed configuration and an expanded configuration and disposed aboutthe microwave radiating portion of the flexible coaxial cable isprovided, wherein the mesh structure expands radially outward from theflexible microwave catheter thereby positioning the at least onefeedpoint at the radial center of the mesh structure. In some aspects,the mesh structure of the flexible microwave catheter includes aconductive material that reduces propagation of denervation energy fromthe microwave radiating portion in an axial direction.

In some aspects, the mesh structure comprises an elastomeric balloonhaving a conductive pattern disposed on an inner surface thereof. Insome aspects, the elastomeric balloon in an expanded configurationpositions the at least one feed point at the radial center of the meshstructure. In some aspects, the conductive pattern defines a window onthe inner surface of the elastomeric balloon, wherein the window ischaracterized by a lack of the conductive pattern. In some aspects, themesh structure and the at least one feed point form a circumferentiallybalanced resonating structure. In some aspects, the mesh structurefurther includes a distal conductive end-cap mesh, a proximal conductiveend-cap mesh, and a tubular mesh body formed between the distal end-capmesh and the proximal end-cap mesh, wherein the distal conductiveend-cap mesh and proximal conductive end-cap mesh reduce propagation ofmicrowave energy from the microwave radiating portion in an axialdirection. In some aspects, the tubular mesh body defines a window thatradiates energy over 360 degrees along a longitudinal span of about 2 cmto about 3 cm.

In another aspect of the present disclosure, a flexible microwavecatheter is provided having a flexible coaxial cable having an innerconductor, an inner dielectric coaxially disposed about the innerconductor, and an outer conductor coaxially disposed about the innerdielectric. At least one feed gap defines a microwave radiating portionof the flexible coaxial cable. A centering structure is disposedadjacent to the microwave radiating portion of the flexible coaxialcable and has a collapsed configuration and an expanded configurationwherein the centering structure extends radially outward from theflexible microwave catheter thereby positioning the at least onefeedpoint at the radial center of the centering structure.

In some aspects, the centering structure of the flexible microwavecatheter includes a stent-like expandable element that expands to atubular shape when distally advanced from the confides of an outersheath of the flexible microwave catheter. In some aspects, thestent-like expandable element defines a plurality of windows thatradiate energy over 360 degrees along a longitudinal span. In someaspects, the centering structure includes a plurality of centeringdevices, at least one of the plurality of centering devices beingdisposed distal each of the at least one feed gaps and at least one ofthe plurality of centering devices being disposed proximal each of theat least one feed gaps. In some aspects, the plurality of centeringdevices reduces propagation of microwave energy from each of the atleast one feed gaps in an axial direction. In some aspects, the at leastone feed gap includes a first feed gap and a second feed gap and thecentering structure further includes a first centering device operablyassociated with the first feed gap, and a second centering deviceoperably associated with the second feed gap, wherein in the expandedconfiguration the first feed gap is at the radial center of the firstcentering device and the second feed gap is at the radial center of thesecond centering device. In some aspects, the first centering device andthe second centering device each define a window therein that radiatesmicrowave energy therethrough.

In some aspects, the centering structure includes an inflatable balloonhousing, and a plurality of lobes formed on the inflatable balloonhousing, wherein in an expanded configuration, a channel is formedbetween adjacent lobes of the plurality of lobes. In some aspects, thecentering structure includes a plurality of fins equally spaced aboutthe circumference of the flexible microwave catheter, wherein in acollapsed configuration the plurality of fins is restrained within anouter sheath of the flexible microwave catheter and in an expandedconfiguration the plurality of fins extends radially outward from theflexible microwave catheter. In some aspects, the plurality of fins isdimensioned to self-center the flexible microwave catheter in a fluidflow lumen via fluid/hydrodynamic forces generated by fluid flowingthrough the fluid flow lumen.

In some aspects, the centering structure includes a centering basket.The centering basket includes a first receiver for engaging the flexiblemicrowave catheter, a second receiver for engaging the flexiblemicrowave catheter, and a plurality of bands extending between the firstreceiver and the second receiver, each of the plurality of bands bowingoutwardly and forming an arcuate path between the first receiver and thesecond receiver. In the collapsed configuration, the plurality of bandsis compressed radially inwardly thereby elongating the centering basket.In an expanded configuration, the plurality of bands is uncompressed andextends radially outwardly. In some aspects, the first receiver fixedlyengages the flexible microwave catheter and the second receiver slidablyengages the flexible microwave catheter.

In some aspects, the centering structure includes at least two centeringbaskets. Each of the at least two centering baskets includes a firstreceiver for engaging the flexible microwave catheter, a second receiverfor engaging the flexible microwave catheter, and a plurality of bandsextending between the first receiver and the second receiver, each ofthe plurality of bands bowing outwardly and forming an arcuate pathbetween the first receiver and the second receiver. In the collapsedconfiguration, the plurality of bands is compressed radially inwardlythereby elongating the centering basket and in an expanded configurationthe plurality of bands is uncompressed and extends radially outwardly.In some aspects, the first receiver fixedly engages the flexiblemicrowave catheter and the second receiver slidably engages the flexiblemicrowave catheter. In some aspects, one of the at least one feed gapsis located between a first and a second of the at least two centeringbaskets.

In some aspects, the centering structure includes a plurality of paddlesequally spaced about the circumference of the flexible microwavecatheter. Each of the plurality of paddles is hingedly attached to theflexible microwave catheter, wherein in a collapsed configuration theplurality of paddles is adjacent and parallel the flexible microwavecatheter and in expanded configuration the plurality of paddles extendsperpendicular to, and extending radially outwardly from, the flexiblemicrowave catheter.

In some aspects, the centering structure includes a plurality of helicalribs connected to the outer surface of the flexible microwave catheteran extending about the outer surface of the flexible microwave catheterin a helical-like fashion, wherein in collapsed configuration theplurality of helical ribs is compressed between the flexible coaxialcable and an inner surface of the outer sheath of the flexible microwavecatheter and in an expanded configuration, the plurality of helical ribsextends radially from the flexible coaxial cable.

In yet another aspect of the present disclosure, a coupler for couplinga coaxial flexible cable, a fluid cooling system, and the outer sheathof a catheter, is provided. The coupler includes a fluid coupler bodyhaving a fluid inlet formed in the fluid coupler body and configured tooperably couple to a source of cooling fluid and receive fluidtherefrom, a fluid outlet formed in the fluid coupler body andconfigured to operably couple to a fluid discharge, a bypass bulbforming an aperture for slidably coupling with a coaxial cable, and anouter sheath coupler forming an aperture for coupling with an outersheath of a catheter while forming a fluid-tight seal therewith. Thecoupler includes a fluid sealing system housed in the fluid coupler bodyhaving a distal sealing diaphragm configured to form a fluid-tight sealabout an outer surface of an inflow lumen and a fluid-tight seal with aninterior surface of the fluid coupler body defining an outflow plenum influid communication with the fluid outlet, the outflow plenum formedbetween a distal interior surface of the fluid coupler body, the outersurface of the inflow lumen, a distal side of the distal sealingdiaphragm and the outer sheath coupler. The coupler includes a proximalsealing diaphragm configured to form a fluid-tight seal about an outersurface of the coaxial cable and a fluid-tight seal with an interiorsurface of the fluid coupler body thereby forming an inflow plenum influid communication with the fluid inlet, the outflow plenum formedbetween a proximal interior surface of the fluid coupler body, and aproximal side of the distal sealing diaphragm, a proximal side of theproximal sealing diaphragm.

In some aspects, the catheter is coaxially formed about the inner lumen,the inner lumen is coaxially formed about the coaxial cable, and theinflow plenum is in fluid communication with a fluid passageway formedbetween the outer surface of the coaxial cable and the inner surface ofthe inflow lumen. In some aspects, the catheter is coaxially formedabout the inner lumen, the inner lumen is coaxially formed about thecoaxial cable, the outflow plenum is in fluid communication with a fluidpassageway formed between the outer surface of the inflow lumen and theinner surface of the outer sheath.

In some aspects, the catheter is coaxially formed about the inner lumen,the inner lumen is coaxially formed about the coaxial cable, the inflowplenum is in fluid communication with a fluid passageway formed betweenthe outer surface of the coaxial cable and the inner surface of theinflow lumen, and the outflow plenum is in fluid communication with afluid passageway formed between the outer surface of the inflow lumenand the inner surface of the outer sheath. In some aspects, the fluidcoupler body slidably engages the coaxial cable.

In yet another aspect of the present disclosure, a microwave energydelivery device is provided. The microwave energy delivery deviceincludes a coaxial feedline having an inner conductor, an innerdielectric insulator coaxially disposed about the inner conductor, andan outer conductor coaxially disposed about the inner dielectric. Themicrowave energy delivery device includes a radiating portion operablycoupled to a distal end of the coaxial feedline. The radiating portionincludes a radiating portion inner conductor operably coupled to andextending from a distal end of the coaxial feedline inner conductor; ashielding outer conductor helically wrapped about the radiating portioninner conductor and operably coupled to the coaxial feedline outerconductor, and a shielding dielectric positioned between the radiatingportion inner conductor and the shielding outer conductor. The width ofthe shielding outer conductor varies according to the longitudinalposition thereof along the coaxial feedline inner conductor. A capoperably couples to a distal end of the radiating portion innerconductor and the shielding outer conductor, and provides an electricalconnection therebetween.

In some aspects, the microwave energy delivery device includes atemperature sensor disposed at a distal end thereof. In some aspects, aradiation pattern generated by the radiating portion is related to atleast one of the variable width of the shielding outer conductor, or avariable helix angle of the shielding outer conductor.

In some aspects, the microwave energy delivery device includes a feedgap defined by a void formed between adjacent wraps of the shieldingouter conductor. In some aspects, a feed gap ratio, defined by the ratioof a feed gap circumference and a shielding outer conductorcircumference along a cross section, changes linearly from a proximalend of the shielding outer conductor to a distal end of the shieldingouter conductor. In some aspects, the feed gap ratio changesnon-linearly from a proximal end of the shielding outer conductor to adistal end of the shielding outer conductor. In some aspects, the feedgap ratio varies between 0% at the proximal end of the radiating portionand about 50% at the distal end of the radiating portion. In someaspects, the feed gap ratio varies between 0% on the proximal end of theradiating portion and about 100% on the distal end of the radiatingportion.

In some aspects, the microwave energy delivery device generates ahelical-shaped electromagnetic field that extends along the longitudinallength of the radiating portion. In some aspects, the helical-shapedelectromagnetic field is related to a void formed between the individualwraps of the shielding outer conductor. In some aspects, the shieldingouter conductor includes at least two helix turns. In some aspects, thecap provides an electrical connection between the radiating portioninner conductor and the shielding outer conductor.

In yet another aspect of the present disclosure, a microwave energydelivery device is provided that includes a coaxial feedline having aninner conductor, an inner dielectric insulator coaxially disposed aboutthe inner conductor, and an outer conductor coaxially disposed about theinner dielectric. The microwave energy delivery device includes aradiating portion operably coupled to a distal end of the coaxialfeedline that includes a radiating portion inner conductor operablycoupled to and extending from a distal end of the coaxial feedline innerconductor, a shielding outer conductor helically wrapped about theradiating portion inner conductor and operably coupled to the coaxialfeedline outer conductor, a shielding dielectric positioned between theradiating portion inner conductor and the shielding outer conductor. Thehelix angle of the shielding outer conductor varies according to thelongitudinal position thereof along the coaxial feedline innerconductor. A cap operably couples to a distal end of at least one of theradiating portion inner conductor and the shielding outer conductor.

In some aspects, the microwave energy delivery device includes a feedgap defined by a void formed between adjacent wraps of the shieldingouter conductor. In some aspects, a feed gap ratio, defined by the ratioof a feed gap circumference and a shielding outer conductorcircumference along a cross section, change linearly from a proximal endof the shielding outer conductor to a distal end of the shielding outerconductor. In some aspects, the feed gap ratio changes non-linearly froma proximal end of the shielding outer conductor to a distal end of theshielding outer conductor. In some aspects, the feed gap ratio variesbetween 0% at the proximal end of the radiating portion and about 50% atthe distal end of the radiating portion. In some aspects, the microwaveenergy delivery device generates a helical-shaped electromagnetic fieldthat extends along the longitudinal length of the radiating portion. Insome aspects, the helical-shaped electromagnetic field is related to avoid formed between the individual wraps of the shielding outerconductor. In some aspects, a cap provides an electrical connectionbetween the radiating portion inner conductor and the shielding outerconductor.

In still another aspect of the present disclosure, a microwave energydelivery device is provided that includes a coaxial feedline having aninner conductor, an inner dielectric insulator coaxially disposed aboutthe inner conductor, and an outer conductor coaxially disposed about theinner dielectric. The disclosed microwave energy delivery deviceincludes a radiating portion operably coupled to a distal end of thecoaxial feedline. The radiating portion includes a radiating portioninner conductor operably coupled to and extending from a distal end ofthe coaxial feedline inner conductor, a shielding outer conductorhelically wrapped about the radiating portion inner conductor andoperably coupled to the coaxial feedline outer conductor, and ashielding dielectric positioned between the radiating portion innerconductor and the shielding outer conductor. The pitch of the helixangle of the shielding outer conductor varies according to thelongitudinal position thereof along the coaxial feedline innerconductor. A cap is operably coupled to a distal end of at least one ofthe radiating portion inner conductor and the shielding outer conductor.

In some aspects, the microwave energy delivery includes a feed gapdefined by a void formed between adjacent wraps of the shielding outerconductor. In some aspects, a feed gap ratio, defined by the ratio of afeed gap circumference and a shielding outer conductor circumferencealong a cross section, changes linearly from a proximal end of theshielding outer conductor to a distal end of the shielding outerconductor. In some aspects, the feed gap ratio changes non-linearly froma proximal end of the shielding outer conductor to a distal end of theshielding outer conductor. In some aspects, the feed gap ratio variesbetween 0% at the proximal end of the radiating portion and about 50% atthe distal end of the radiating portion. In some aspects, the microwaveenergy delivery device generates a helical-shaped electromagnetic fieldthat extends along the longitudinal length of the radiating portion. Insome aspects, the helical-shaped electromagnetic field is related to avoid formed between the individual wraps of the shielding outerconductor. In some aspects, the cap provides an electrical connectionbetween the radiating portion inner conductor and the shielding outerconductor.

In yet another aspect of the present disclosure, a method for forming aresonating structure within a body lumen is provided. The methodincludes advancing a flexible microwave catheter with a body lumen of apatient, the flexible microwave catheter including a radiating portionon the distal end of the flexible microwave catheter, the radiatingportion configured to receive a microwave energy signal at a microwavefrequency, and at least one centering device adjacent the radiatingportion and configured to deploy radially outward from the flexiblemicrowave catheter. The radiating portion is positioning adjacent atargeted tissue. At least one centering device is deployed radiallyoutward from the flexible microwave catheter and within the body lumento position the radiating portion at the radial center of the bodylumen. A circumferentially balanced resonating structure is formedwithin the body lumen via the radiating portion, and a microwave energysignal at the microwave frequency is delivered from the radiatingportion, and resonates the body lumen at the microwave frequency.

In some aspects, the circumferentially balanced resonating structureradiates energy over 360 degrees along a longitudinal span of about 2 cmto about 3 cm. In some aspects, body lumen is the renal artery. In someaspects, the targeted tissue is the renal nerve and thecircumferentially balanced resonating structure generates anelectromagnetic field that denervates the targeted tissue.

In some aspects, the method further including the steps of providing acontinuous fluid flow with the body lumen, and cooling at least aportion of the body lumen. In some aspects, the method further includesthe step of continuing the delivery of the microwave energy signal untila sufficient amount of energy has been delivered to effectively damagethe targeted tissue while preserving the critical structure of the bodylumen.

In some aspects, the method further includes the steps of monitoring thetemperature of the continuous fluid flow, and terminating the deliveryof microwave energy if the monitored temperature exceeds a thresholdtemperature.

In some aspects, the body lumen is selected from at least one of agastrointestinal lumen, an auditory lumen, a respiratory system lumen,urinary system lumen, a female reproductive system lumen, a malereproductive system lumen, a vascular system lumen, and an internalorgan.

In some aspects, the method further includes expanding the body lumen toform a structure related to the microwave frequency.

In some aspects, the method further includes selecting the microwavefrequency to resonate the body lumen based on the anatomical structureof the body lumen.

In some aspects, the method further includes monitoring a temperaturewithin the body lumen, and terminating the delivery of the microwaveenergy signal when the temperature exceeds a threshold temperature.

In some aspects, the radiating portion includes a feed gap forming anopen circuit in the flexible microwave catheter. In some aspects, theradiating portion includes includes a first feed gap and a second feedgap wherein the first and second feed gaps each form open circuits inthe flexible microwave catheter.

In still another aspect of the present disclosure, a method for forminga resonating structure within a body lumen is presented. The presentedmethod includes advancing a flexible microwave catheter with a bodylumen of a patient. The flexible microwave catheter includes a radiatingportion on the distal end of the flexible microwave catheter that isconfigured to receive a microwave energy signal at a microwavefrequency, an electrically conductive mesh adjacent the radiatingportion, and a retractable sheath configured to deploy the electricallyconductive mesh about the radiating portion. The method includespositioning the radiating portion adjacent a targeted tissue, retractingthe retractable sheath, deploying the electrically conductive meshradially outward from the flexible microwave catheter and within thebody lumen thereby centering the radiating portion at the radial centerof the body lumen, forming a circumferentially balanced resonatingstructure within the body lumen via the radiating portion, anddelivering the microwave energy signal at the microwave frequency toresonate the body lumen at the microwave frequency.

In some aspects, the method includes forming a window in theelectrically conductive mesh, the window being characterized by a lackof material, and heating a region of the body lumen related to thewindow. In some aspects, the body lumen is a renal artery, the targetedtissue is a renal nerve, and heating the region of the body lumenrelated to the window at least partially denervates the kidney.

In some aspects, the method includes the step of cooling at least aportion of the renal artery.

In some aspects, the method includes the steps of providing a fluidcooling structure to enhance energy delivery and reduce heating of aleast a portion of the flexible microwave catheter. The body lumen maybe selected from at least one of a gastrointestinal lumen, an auditorylumen, a respiratory system lumen, urinary system lumen, a femalereproductive system lumen, a male reproductive system lumen, a vascularsystem lumen, and an internal organ. In some aspects, thecircumferentially balanced resonating structure radiates energy over 360degrees along a longitudinal span of about 2 cm to about 3 cm.

In yet another aspect of the present disclosure, a method forimplementing a microwave ablation waveguide is provided. The methodincludes the steps of selecting a lumen adapted to convey a fluid andformed from living biological tissue, longitudinally introducing anelongate inner conductor into the lumen, positioning a distal end of theelongate inner conductor at a location within the lumen adjacent to ananatomical feature of interest, centering at least a portion of theelongate inner conductor along the longitudinal axis of the lumen,energizing the elongate inner conductor with microwave ablation energy,and electrically shielding, with the lumen, the elongate inner conductorto reduce propagation of microwave ablation energy proximally of theanatomical feature of interest. In some aspects, the lumen is selectedin accordance with a dielectric property of the fluid conveyed therein.

In some aspects, the centering step includes providing a centeringmember which facilitates the flow of the conveyed fluid therethrough. Insome aspects, the method further includes the step of altering adielectric property of the conveyed fluid. In some aspects, the methodfurther includes the step of introducing a fluid amendment into theconveyed fluid. In some aspects, the fluid amendment is introduced intothe conveyed fluid in response to a sensed electrical parameter. Thesensed electrical parameter may be selected from the group consisting ofa VSWR, a power factor, an impedance, a capacitance, an inductance, anda resistance. In some aspects, the fluid amendment is introduced intothe conveyed fluid in response to a sensed biological parameter. Thesensed biological parameter may be selected from the group consisting ofa tissue temperature, a blood pressure, a heart rate, a respiratoryrate, a tissue impedance, a blood oxygenation, and a neural response. Insome aspects, the fluid amendment may be introduced into the conveyedfluid at continuous rate. In some aspects, the fluid amendment isintroduced into the conveyed fluid at variable rate. The fluid amendmentmay be introduced into the conveyed fluid at a rate selected in responseto a sensed electrical parameter and/or a sensed biological parameter.

In still another aspect of the present disclosure, a method of using amicrowave ablation instrument having a radiation pattern is provided.The method includes selecting a lumen adapted to convey a fluid andformed from living biological tissue, longitudinally introducing themicrowave ablation pattern into the lumen, positioning the radiationpattern of the microwave ablation instrument at a location adjacent toan anatomical feature of interest, energizing the microwave ablationinstrument with microwave ablation energy, and electrically shielding,with the lumen, the microwave ablation instrument to reduce propagationof microwave ablation energy along the lumen proximally of theanatomical feature of interest.

In some aspects of the method, the lumen is selected in accordance witha dielectric property of the fluid conveyed therein. In some aspects,the method includes altering a dielectric property of the conveyedfluid. In some aspects, the method includes introducing a fluidamendment into the conveyed fluid. In some aspects, the fluid amendmentis introduced into the conveyed fluid in response to a sensed electricalparameter. In some aspects the sensed electrical parameter is selectedfrom the group consisting of a VSWR, a power factor, an impedance, acapacitance, an inductance, and a resistance. In some aspects, the fluidamendment is introduced into the conveyed fluid in response to a sensedbiological parameter. In some aspects, the sensed biological parameteris selected from the group consisting of a tissue temperature, a bloodpressure, a heart rate, a respiratory rate, a tissue impedance, a bloodoxygenation, and a neural response.

In yet another aspect of the present disclosure, a method forimplementing a microwave ablation waveguide is provided. The methodincludes the steps of selecting a lumen adapted to convey a fluid andformed from living biological tissue, introducing an elongate innerconductor into the lumen, positioning at least a portion of the elongateinner conductor within the lumen such that a longitudinal axis of theelongate inner conductor is positioned substantially parallel to and ata desired distance from a longitudinal axis of the lumen and proximatean anatomical feature of interest, and transferring microwave energyalong the elongate inner conductor such that the lumen shields the innerconductor and allows a predetermined amount of microwave energy topropagate through the anatomical feature of interest. In some aspects ofthe method, the lumen is selected in accordance with a dielectricproperty of the fluid conveyed therein. In some aspects, the methodincludes altering a dielectric property of the conveyed fluid. In someaspects, the method includes introducing a fluid amendment into theconveyed fluid. In some aspects, the fluid amendment is introduced intothe conveyed fluid in response to a sensed electrical parameter. In someaspects the sensed electrical parameter is selected from the groupconsisting of a VSWR, a power factor, an impedance, a capacitance, aninductance, and a resistance. In some aspects, the fluid amendment isintroduced into the conveyed fluid in response to a sensed biologicalparameter. In some aspects, the sensed biological parameter is selectedfrom the group consisting of a tissue temperature, a blood pressure, aheart rate, a respiratory rate, a tissue impedance, a blood oxygenation,and a neural response.

In still another aspect of the present disclosure, a method of using amicrowave ablation instrument is provided. The method includes selectinga lumen adapted to convey a fluid and formed from living biologicaltissue, introducing a microwave antenna having an outer conductor with astructure capable of producing a predefined radiation pattern into thelumen, positioning the microwave antenna at a location proximate ananatomical feature of interest, and energizing the microwave antennawith microwave energy such that as the microwave energy emanates fromthe microwave antenna in the predetermined radiation pattern, the lumencontrols the amount of microwave energy allowed to propagatetherethrough. In some aspects of the method, the lumen is selected inaccordance with a dielectric property of the fluid conveyed therein. Insome aspects, the method includes altering a dielectric property of theconveyed fluid. In some aspects, the method includes introducing a fluidamendment into the conveyed fluid. In some aspects, the fluid amendmentis introduced into the conveyed fluid in response to a sensed electricalparameter. In some aspects the sensed electrical parameter is selectedfrom the group consisting of a VSWR, a power factor, an impedance, acapacitance, an inductance, and a resistance. In some aspects, the fluidamendment is introduced into the conveyed fluid in response to a sensedbiological parameter. In some aspects, the sensed biological parameteris selected from the group consisting of a tissue temperature, a bloodpressure, a heart rate, a respiratory rate, a tissue impedance, a bloodoxygenation, and a neural response.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in, and constitute apart of this specification, illustrate various example embodiments ofthe present disclosure. Together with the general description givenabove, and the detailed description of the embodiments given below, theaccompanying drawings serve to explain the principles of the system,apparatus and methods disclosed herein.

FIG. 1 is a partial cross-sectional view of a flexible microwavecatheter accessing the renal artery via the vascular system according tosome embodiments of the present disclosure;

FIG. 2 is a system diagram of a microwave energy delivery system havinga flexible microwave catheter according to some embodiments of thepresent disclosure;

FIG. 3 is a partial cross-sectional view of a flexible microwavecatheter accessing the renal artery via the vascular system inaccordance with some embodiments of the present disclosure;

FIG. 4A is a transverse cross-sectional view of the anatomical structureof a renal artery;

FIG. 4B is a transverse cross-sectional view of an embodiment of aflexible coaxial cable in accordance with some embodiments of thepresent disclosure;

FIG. 4C is a transverse cross-sectional view of an embodiment of amicrowave waveguide structure within a natural body lumen in accordancewith some embodiments of the present disclosure;

FIG. 5 is a longitudinal cross-section of an embodiment of a microwavewaveguide structure in accordance with some embodiments of the presentdisclosure;

FIG. 6A is a block diagram of a catheter hub according to someembodiments of the present disclosure;

FIG. 6B is a transverse cross-section of an embodiment of a flexiblemicrowave catheter according to some embodiments of the presentdisclosure;

FIG. 7 is a system diagram of an embodiment of a microwave energydelivery system in accordance with some embodiments of the presentdisclosure having a flexible microwave catheter with at least a part ofthe radiating portion housed in the outer sheath of the flexiblemicrowave catheter;

FIGS. 8A-8C illustrate embodiments of longitudinal cross-sections ofcatheter hub couplers according to some embodiments of the presentdisclosure;

FIG. 9A is a side view of an embodiment of a flexible microwave catheterguide wire system according to some embodiments of the presentdisclosure;

FIGS. 9B-9C are longitudinal cross-sectional diagrams of the guide wiresystem of FIG. 9A;

FIGS. 10A-10B are longitudinal and transverse cross-sections,respectively, of an embodiment of a flexible microwave catheter centeredin a renal artery in accordance with some embodiments of the presentdisclosure;

FIGS. 11A-11B are longitudinal and transverse cross-sections,respectively, of a flexible microwave catheter in an off-center positionwithin a renal artery;

FIGS. 12A-12B are longitudinal and transverse cross-sections,respectively, of a flexible microwave catheter in an off-center positionwithin a renal artery;

FIG. 13 illustrates a relationship between temperatures measured insideand outside the renal artery and power measured during an experimentalprocedure;

FIGS. 14A-14F illustrates steps of a manufacturing process forassembling some of the embodiments of the present disclosure;

FIG. 15A is a longitudinal, cross-sectional view of an embodiment of aradiating portion cap in accordance with the present disclosure forreturning circulating fluid from an inflow fluid passageway to anoutflow fluid passageway;

FIG. 15B is a perspective view with partial cross-section of the cap ofFIG. 15A;

FIGS. 16A-16B are longitudinal, cross-sectional views of embodiments ofstent-like expandable elements associated with a radiating portion inaccordance with some embodiments of the present disclosure;

FIG. 16C is a side view of an embodiment of a stent-like expandableelement associated with a radiating portion in accordance with someembodiments of the present disclosure;

FIG. 17A is a perspective view of an embodiment of a conductive meshstructure that defines a plurality of windows for selectively deliveringdenervation energy to tissue in accordance with some embodiments of thepresent disclosure;

FIG. 17B is a perspective view of a portion of a renal artery afterreceiving the selectively delivered denervation energy from theconductive mesh structure of FIG. 17A;

FIG. 18A is a perspective view of an embodiment of a conductive meshstructure that defines a window for selectively delivering denervationenergy to tissue in accordance with some embodiments of the presentdisclosure;

FIGS. 18B-18G are perspective views illustrating steps of a surgicalprocedure in accordance with some embodiments of the present disclosureutilizing the conductive mesh structure of FIG. 18A;

FIG. 19A is a perspective view of an embodiment of a conductive meshstructure that defines a plurality of windows for selectively deliveringdenervation energy to tissue in accordance with some embodiments of thepresent disclosure;

FIG. 19B is a perspective view of a portion of a renal artery afterreceiving selectively delivered denervation energy from the conductivemesh structure of FIG. 19A;

FIG. 20 is a side view of an embodiment of a radiating portion inaccordance with some embodiments of the present disclosure having aplurality of conductive mesh structures each defining a window forselectively delivering denervation energy to tissue;

FIG. 21 is a side view of an embodiment of a radiating portion inaccordance with some embodiments of the present disclosure having aplurality of conductive mesh structures that define a plurality ofradiating portions;

FIG. 22A is a side view of an embodiment of a radiating portion inaccordance with some embodiments of the present disclosure having adistal mesh basket structure and a proximal mesh structure;

In FIG. 22B is a side view of an embodiment of a radiating portion inaccordance with some embodiments of the present disclosure having aproximal mesh structure and a distal mesh basket structure operablycoupled to the cap via a tether;

FIG. 23 is a perspective view of an embodiment of a stepped flexiblemicrowave catheter with a stepped diameter in accordance with someembodiments of the present disclosure;

FIG. 24 is a side view of a radiating portion of an embodiment of aflexible microwave catheter that includes an inflatable centeringballoon in accordance with some embodiments of the present disclosure;

FIG. 25A is a longitudinal, cross-sectional view of an embodiment of amicrowave energy delivery system having a distal radiating portionwithin an inflatable balloon in accordance with some embodiments of thepresent disclosure;

FIG. 25B is a transverse, cross-sectional view of an embodiment of thedistal radiating portion of the microwave energy delivery system of FIG.25A;

FIG. 26A is a perspective view of an embodiment of an inflatable balloonhaving a plurality of lobes for centering a radiating portion in a bodylumen in accordance with some embodiments of the present disclosure;

FIG. 26B is a transverse, cross-sectional view of the inflatable balloonof FIG. 26A;

FIG. 26C is a perspective view of the housing of the inflatable balloonof FIG. 26A;

FIGS. 27A-27B are longitudinal and transverse cross-sectional views,respectively, of a centering device housed in the outer sheath of theflexible microwave catheter in accordance with some embodiments of thepresent disclosure;

FIG. 27C is a longitudinal cross-sectional view of an embodiment of acentering device deployed from the outer sheath of a flexible microwavecatheter in accordance with some embodiments of the present disclosure;

FIG. 27D is a perspective view of the centering device of FIGS. 27A-27Cin a deployed position;

FIG. 28 is a perspective view of an embodiment of a four-prong centeringdevice in accordance with some embodiments of the present disclosure;

FIG. 29 is perspective view of an embodiment of a centering basketadapted to center a radiating portion of a distal portion of a flexiblemicrowave catheter in accordance with some embodiments of the presentdisclosure;

FIG. 30 is perspective view of an embodiment of a centering basketadapted to center a radiating portion of a flexible microwave catheterproximal the radiating portion in accordance with some embodiments ofthe present disclosure;

FIG. 31 is perspective view of an embodiment of a centering basketadapted to center a radiating portion in accordance with someembodiments of the present disclosure;

FIG. 32A is a perspective view of an embodiment of a proximal centeringbasket and a distal centering basket operably coupled to the distal endof a flexible microwave catheter in accordance with some embodiments ofthe present disclosure;

FIG. 32B is a perspective view of an embodiment of a proximal centeringbasket and a distal centering basket operably coupled to the distal endof a flexible microwave catheter in accordance with some embodiments ofthe present disclosure;

FIG. 33 is a perspective view of an embodiment of a dual-band centeringdevice centered on the radiating portion in accordance with someembodiments of the present disclosure;

FIG. 34 is a perspective view of an embodiment of a clover-leafcentering device including a plurality of petals for centering aradiating portion in accordance with some embodiments of the presentdisclosure;

FIG. 35 is a perspective view of an embodiment of the distal end of aflexible microwave catheter including a clover-leaf centering device anda centering basket in accordance with some embodiments of the presentdisclosure;

FIGS. 36A and 36B are perspective views of an embodiment of a deployablepaddle centering device in accordance with some embodiments of thepresent disclosure;

FIGS. 37A and 37B are perspective views of an embodiment of a deployabledual paddle centering device in accordance with some embodiments of thepresent disclosure;

FIGS. 38A and 38B are perspective views of an embodiment of a deployablepaddle centering device in accordance with some embodiments of thepresent disclosure;

FIGS. 39A and 39B are perspective views of an embodiment of deployabledual paddle centering device in accordance with some embodiments of thepresent disclosure;

FIGS. 40A and 40B are perspective views of an embodiment of a deployablecentering device with a plurality of tines in accordance with someembodiments of the present disclosure;

FIGS. 41A and 41B are perspective views of an embodiment of a helicalcentering devices in accordance with some embodiments of the presentdisclosure;

FIG. 42 is a side view of a distal portion of the FIG. 7 embodiment of amicrowave energy radiating device having a portion of the outer sheathremoved and having a configurable portion in a fully retracted position;

FIG. 43 is a side view of a distal portion of the FIG. 7 embodiment of amicrowave energy radiating device having a portion of the outer sheathremoved and having a configurable portion in a partially deployedposition;

FIG. 44 is a side view of the distal portion of the FIG. 7 embodiment ofa microwave energy radiating device having a portion of the outer sheathremoved and having a configurable portion in a fully deployed position;

FIG. 45 is a side, perspective view of an embodiment of a microwaveenergy radiating device having a non-linear wrap pattern in accordancewith some embodiments of the present disclosure;

FIG. 46 is a top, perspective view of the outer conductor of the FIG. 45embodiment having been removed therefrom;

FIG. 47 is a side, perspective view of an embodiment of a microwaveenergy radiating device having a non-linear wrap pattern according toanother embodiment of the present disclosure;

FIG. 48 is a top, perspective view of the outer cover of the FIG. 47embodiment having been removed therefrom;

FIG. 49 is a graph illustrating a ratio of a radiating portion to anon-radiating portion of the microwave energy radiating devices of FIGS.44, 45 and 47;

FIG. 50 is an electrical circuit diagram of an embodiment of a leakywaveguide according to the present disclosure;

FIG. 51 illustrates an embodiment of a leaky waveguide having a varyingslot width according to the present disclosure;

FIG. 52 is an electrical diagram of an embodiment of a ten-slotwaveguide in accordance with the present disclosure illustrating theavailable energy for each slot and the percentage of the availableenergy transmitted from each slot;

FIG. 53 is a side view of an embodiment of a ten-slot waveguide inaccordance with the present disclosure wherein each slot transmits asubstantially similar amount of energy,

FIG. 54 is a side view of an embodiment of a helix waveguide with tenhelix wraps according to embodiments of the present disclosure,

FIG. 55 is a perspective view of a five-slot waveguide according toembodiments of the present disclosure;

FIG. 56 is a perspective view of a helix waveguide with five helix wrapsaccording to embodiments of the present disclosure;

FIG. 57 is a side-by-side comparison of a five-slot waveguide and ahelix waveguide with five helix wraps according to embodiments of thepresent disclosure.

FIG. 58A is a perspective view of an embodiment of a balloon centeringdevice in a deflated configuration with a spiral window formed thereinin accordance with some embodiments of the present disclosure;

FIG. 58B is a perspective view in partial cross-section of the ballooncentering device of FIG. 58A in a fully inflated configuration andpositioned in the renal artery via the vascular system; and

FIG. 58C is a perspective view of a portion of a renal artery afterreceiving selectively delivered denervation energy from the ballooncatheter of FIGS. 58A-58C.

DETAILED DESCRIPTION

Particular embodiments of the present disclosure are describedhereinbelow with reference to the accompanying drawings; however, thedisclosed embodiments are merely examples of the disclosure, which maybe embodied in various forms. Well-known and/or repetitive functions andconstructions are not described in detail to avoid obscuring the presentdisclosure in unnecessary or redundant detail. Therefore, theterminology used herein for the purpose of describing particularembodiments, specific structural and functional details disclosedherein, as well as the specific use disclosed herein, are not to beinterpreted as limiting, but merely as a basis for the claims and as arepresentative basis for teaching one skilled in the art to variouslyemploy the present disclosure in virtually any appropriately detailedstructure. In this description, as well as the drawings, like-referencednumbers represent elements which may perform the same, similar, orequivalent functions.

As used herein, the term “proximal,” as is traditional, shall refer tothe end of the instrument that is closer to the user, while the term“distal” shall refer to the end that is farther from the user. As usedherein, terms referencing orientation, e.g., “top”, “bottom”, “up”,“down”, “left”, “right”, “o'clock”, and the like, are used forillustrative purposes with reference to the figures and correspondingaxes and features shown therein. It is to be understood that embodimentsin accordance with the present disclosure may be practiced in anyorientation without limitation.

As discussed hereinabove, a flexible microwave catheter may be used toperform a procedure by utilizing a natural or artificial lumen. Oneparticular procedure discussed herein is a denervation procedure thatutilizes the vascular system to access a kidney. Embodiments aredisclosed herein whereby the energy and antenna characteristics aredesigned to enable application of microwave denervation energy to atargeted neurological structure, such as without limitation, asympathetic nerve bundle surrounding a renal artery, although thedevices and methods may be utilized in any other procedure and on anyother body lumen, organ or bodily structure. This particular procedureis only used to demonstrate general concepts and the use of someembodiments in accordance with the present disclosure. For example,embodiments of the flexible microwave catheter disclosed herein may alsobe used to perform procedures in the respiratory system, e.g., to treattumors in the upper respiratory tract and the lungs, as well as to treatasthma, chronic obstructive pulmonary disease (COPD) emphysema, etc.

As illustrated in FIG. 1, the disclosed flexible microwave catheter 30is percutaneously introduced into the femoral artery FA through anarterial catheter 110 and positioned within the right renal artery RRAand adjacent to the right renal nerve bundle RRN. The flexible microwavecatheter 30 includes a radiating portion 100 that cooperatesadvantageously with the right and/or left renal artery RRA, LRA(hereinafter, “renal artery RA”) physiology to deliver denervationenergy to the respective right and/or left renal nerve bundles RRN, LRN(hereinafter “renal nerve RN”) while minimizing collateral damage to therespective arterial vessel and related anatomical structures. In thediscussion to follow, the renal nerve RN and the renal artery RA areused to illustrate embodiments in accordance with the present disclosurehowever it is to be understood the disclosed embodiments may be usedwith either the right renal artery RRA or the left renal artery LRA todeliver denervation energy to the respective right renal nerve bundleRRN and left renal nerve bundle LRN.

Elevated sympathetic nerve activity initiates and sustains the elevationof blood pressure. The renal nerve bundle RN include the renalsympathetic nerves (efferent and afferent) that are bundled around therenal artery RA. As such, the renal artery RA facilitates access to therenal nerve bundles RN through the femoral artery FA and/or theabdominal aorta A. The flexible microwave catheter 30 places theradiating portion 100 of a microwave energy applicator in closeproximity to the renal nerve bundles RN. Once positioned in the renalartery RA, the radiating portion 100 can focus energy from within therenal artery RA toward the respective renal nerves bundle RN surroundingthe renal artery RA in an effort to denervate the kidneys and ultimatelyreduce blood pressure.

As discussed in greater detail hereinbelow, the various embodimentsinclude structures that allow for the application of electrosurgicalenergy to one or more locations within the renal artery RA (or otherlumen or body structure) without compromising the overall integrity ofthe vessel wall. In some embodiments, the energy delivery structure doesnot mechanically contact the vessel wall, thereby reducing complicationsfrom perforation or stenosis as a result of mechanical damage. In someembodiments, the energy delivery structure directs energy to aparticular portion of one or more layers of the body lumen/bodystructure thereby maintaining the overall viability of the bodylumen/body structure. In some embodiments blood or fluid flow with thevessel contributes to cooling of inner layers of the vessel wall,thereby reducing unwanted heating and collateral damage to the vesselwall while enabling energy delivery to the outer layer proximate therenal nerves.

The systems, devices and methods described herein provide spatial energycontrol of microwave energy. Spatial energy control incorporates threefactors, namely, repeatability of energy delivery, precise control ofthe delivered energy, and efficient delivery of energy. The factors thatcontribute to spatial energy control include thermal management,dielectric management, buffering, and electrical current control. Thesefactors can be controlled through systems, devices and methods thatoperate in tandem with the surrounding anatomical structure, effectivelyincorporating the surrounding tissue as part of the microwave device.

Microwave energy systems and devices exhibit behaviors that arefundamentally different than behaviors of systems and devices usinglower frequency RF signals. For example, the operation and functionalityof a RF system, using low frequency “RF” signals, requires an electricalcircuit that includes a closed-loop connection of conductive materials,e.g., a completed electrical circuit. The behavior of the circuit isdirectly dependent on the electrical properties of the closed connectionof conductive materials. The most obvious behavior and example beingthat in a RF circuit, a break in the closed-loop connection ofconductive materials, e.g., an open circuit, renders the systeminoperable.

Microwave systems, on the other hand, transmit microwave energy signalsthrough waveguides. The most common example of a waveguide being acoaxial cable that consists of an inner conductor positioned coaxiallywithin an outer conductor by a dielectric. Unlike a RF circuit, creatingan open circuit (e.g., slot) in the coaxial outer conductor does notrender the system inoperable. Instead, the waveguide continues to conveythe microwave signal, and the slot radiates a portion of the energybeing transmitted by the waveguide.

As such, some embodiments of the systems, devices and methods describedherein incorporate a portion of the anatomical structure into the designof the microwave energy delivery system. More specifically, thecylindrical structure of natural body lumens and other body structuresthat are concentric in nature can be utilized to operate in conjunctionwith, and become part of, a waveguide used by the devices describedherein to transmit microwave energy.

The use of the natural lumen structure and/or body structure as acomponent of the radiating structure enables enhanced energy deliverytechniques, such as focusing microwave energy-induced thermal therapy toa targeted anatomy. For example, as noted above structures describedherein are capable of targeting the smooth muscle layer within thebronchus of the lungs, and are capable of targeting the renal nerveswithin the adventitia layer of the renal nerve. Additionally, the use ofthe devices described herein within the lumen structures enables theformation of a directional radiating pattern to specific sections of thelumen.

In some embodiments, the devices described herein also utilize thefluids present in the natural body lumens to perform dielectric loadingof the anatomical radiating structure. The properties of the fluid areincorporated into the design of the microwave radiator as a designcomponent. For example, bodily fluids may form a dielectric layer and/ora conductive layer of an anatomical waveguide and the properties of thefluid are utilized in the design, such as, for example, for impedancematching, energy efficiency, wavelength buffering, and radiation patterncontrol and shaping.

The fluid's dielectric properties may be externally manipulated and/oradjusted by introducing (and/or eliminating) one or more elements intothe fluid. For example, fluids high in water content exhibit a highdielectric constant that enable shaping of microwave fields aroundradiation structures. As such, the dielectric properties of blood may beadjusted by modifying the plasma composition and adjusting the ratio ofwater, protein, inorganic salts, and organic substances. Similarly, thedielectric properties of blood may be adjusted by changing the glucoselevels. In this manner, changing the dielectric property of the fluidsmay effectuate changes in the performance of the devices describedherein, since the bodily fluids can be used as the dielectric layer inthe anatomical waveguides discussed herein.

The systems, devices, and methods described herein also utilize fluids(e.g., natural or externally introduced) within the natural body lumensfor thermal management of one or more layers of the anatomical waveguideand/or one or more components of the devices described herein. Fluidsmitigate thermal damage through fluid cooling of non-target anatomywithin the heating profile of the devices. Additionally, the fluid flowmay be manipulated by adjusting the device(s) (e.g., increasing ordecreasing a blockage thereby decreasing or increasing fluid flow),adjusting the natural flow rate (e.g., directing fluid flow to aparticular body portion by restricting flow at another body portion)and/or adjusting a body function (e.g., elevating the heart rate therebyincreasing the rate of blood flow through the body). Fluid temperaturemay also be manipulated by providing an external or an internal heatsink.

Centering of the devices described herein increases the predictabilityand repeatability of energy delivery to the targeted anatomicalstructures. The centering devices described herein include passivecentering devices (e.g., utilizing the natural flow of fluid in a lumenfor centering) or active devices that actively and/or positivelyposition the radiating portion in the lumen.

In embodiments in accordance with the present disclosure, a microwaveenergy delivery system 12 with a flexible microwave catheter 30 isprovided and illustrated in FIG. 2. Microwave system 12 includes amicrowave generator 22, transmission line 14, a fluid cooling system 40,catheter hub 18 and a flexible microwave catheter 30. Some embodimentsmay include a guide wire 47 for guiding and/or positioning the radiatingportion 100 of the flexible microwave catheter 30 to a desirableposition.

Flexible microwave catheter 30, in accordance with the presentdisclosure, includes a flexible coaxial cable 32, or feedline, that isoperably connectable to the microwave generator 22 (e.g., through thecatheter hub 18 and transmission line 14). Flexible microwave catheter30 includes a radiating portion 100 positioned on a distal-most endthereof. In some embodiments, as discussed hereinbelow and illustratedin the accompanying drawings, the radiating portion 100 is deployablefrom the outer sheath 35 of flexible microwave catheter 30 and includesan exposed cap 33 on the distal-most end thereof.

One or more parameters of the microwave energy signal may be related tothe targeted tissue. In some embodiments, the frequency of the microwaveenergy signal generated by the microwave generator 22 is related to thediameter of the body lumen. For example, the diameter of the renalartery may require a microwave signal at first frequency, the diameterof the esophagus may require a microwave signal at a second frequencyand the diameter of the vaginal cavity may require a microwave signal ata third frequency. Some applications, such as providing treatment to therespiratory system, may require the frequency to vary with the positionof the radiating portion within the body lumen due to the varyingdiameter along the body lumen (e.g., airways).

Catheter hub 18 is disposed at a proximal end of flexible microwavecatheter 30 and is configured to enable the operable coupling of asource of denervating energy (e.g., a microwave generator 22) to thetransmission line 14. Catheter hub 18 provides an exchange of coolingfluid between the flexible microwave catheter 30 and the fluid coolingsystem 40. Fluid cooling system 40 provides a source of coolant to theinflow conduit 42 and receives coolant evacuated from the catheter hub18 through an outflow conduit 43 connected to a fluid receivingdestination (e.g., a receptacle, reservoir, or drain).

FIG. 3 illustrates a flexible microwave catheter 30 in accordance withthe present disclosure positioned in a renal artery RA. In someembodiments, the flexible microwave catheter 30 is maneuvered through along sheath 31 initially positioned in the femoral artery and/or theaorta. A distal end of the long sheath 31 is positioned at a proximalend of the renal artery RA. Flexible microwave catheter 30 is guidedthrough the long sheath 31 and into the renal artery RA, e.g., extendedpast the distal end of the long sheath 31 and positioned within therenal artery RA. In some embodiments, a guide wire 47 may be utilized toguide and/or position the long sheath 31 or the flexible microwavecatheter 30 as described herein.

The radiating portion 100 of the flexible microwave catheter 30 ispositioned within the renal artery RA and receives a microwave energysignal from the microwave generator 22 (see FIG. 2). At least a portionof the microwave energy signal is selectively delivered to at least aportion of the renal artery RA. Some embodiments described herein, andillustrated in the accompanying figures, advantageously utilize therenal artery physiology in the application of microwave energy, therebyinducing modification of the target tissue. With respect to a renaldenervation procedure, the target tissue for treating hypertensionincludes at least a portion of the renal nerves RRN, LRN.

The anatomical structure of a natural body lumen (e.g., a renal arteryRA), is illustrated in FIG. 4A. The innermost layer and/or core of thelumen that forms the fluid pathway of the lumen (e.g., the hollow bodyformed by the lumen). The fluid 1 contained in an artery is typically abodily fluid (e.g., blood) although a non-bodily fluid (e.g., saline,air, or any other suitable fluid) may be utilized and/or introduced.Other natural body lumens may contain other body fluids (e.g., blood,mucus, urine, bile, air, and any combination thereof) or the lumen maycontain an externally-introduced fluid (e.g., air, saline, and water),or any combination thereof.

The first layer of the body lumen (e.g., renal artery RA) is the intimalayer 2 formed of about 50% elastin and about 50% cartilage. Othernatural lumens may include a similar elastin and/or cartilage-like layersuch, as for example, a mucus layer, a mucus membrane layer or thestratum corneum. The second layer of the body lumen (e.g., renal arteryRA) is a smooth muscle layer 3. Examples of other natural lumens thatinclude a layer of smooth muscle are the esophagus, stomach, intestines,brochi, uterus, urethra and the bladder. The third layer in a body lumen(e.g., renal artery RA) is the adventitia layer 4 (a.k.a., the tunicaexterna). Adventitia layer 4 is the outermost connective tissue coveringmost organs, vessels and other body structures. The outermost adventitialayer 4, as with many body lumens, is covered with an outermost fatlayer 5.

While each body lumen and bodily structure is functionally different,the general structures of body lumens and many bodily structures havestructural similarities. For example, the first layer of the esophagealwall is the mucosa (e.g., mucus membrane), the second layer is thesubmucosa which includes esophageal glands, the third layer is themuscularis (e.g., smooth muscle), and the outermost layer is theadventitia layer which is covered by fat. Variations in the natural bodylumens and body structures do not change the general operation of thedevices, systems, and methods described herein, and may only requireslight variations in one or more operational parameters thereof.

FIG. 4B illustrates the coaxial arrangement of a flexible coaxial cable32 that includes an inner conductor 20, a dielectric layer 22 and anouter conductor 24. Drawing an analogy between the structures that forma natural body lumen in FIG. 4A and the structures that form a flexiblecoaxial cable 32 in FIG. 4B, the outer conductor 24 is analogous to theadventitia layer 4 and/or the outermost fat layer 5 and the dielectriclayer 22 is analogous to the fluid 1 in the hollow body.

FIG. 4C illustrates the formation of a microwave waveguide structureRA/32 within a body lumen (e.g., renal artery RA) wherein the microwavestructure RA/32 includes an inner conductor 20 (e.g., conductorpositioned in the hollow body 1), a dielectric (e.g., fluid in thehollow body 1/22) and an outer conductor (e.g., formed from theoutermost fat layer 5/24). As such, when applied with a microwave energysignal, the anatomy becomes part of the microwave waveguide structurewherein the dielectric constant and loss factors are related to thephysiology and composition of the natural body lumen and/or bodilystructure.

Energy losses in any waveguide structure include dielectric losses(e.g., loss through the dielectric material) and conductor losses (e.g.,losses in the conductors forming the waveguide). As such, the dielectriclosses are losses in the anatomy that forms the dielectric (e.g., fluid1 in the hollow body) and conductor losses are losses in the structuresand/or anatomy that form the inner conductor 20 and the outer conductor4/24 and 5/24.

In some embodiments, forming a resonating microwave waveguide structurewith the layers that form the anatomical structure of the renal arterycreates an inefficient waveguide through which the losses in theanatomical structure can heat target tissue to damaging temperaturelevels. For example, the renal nerves LRN, RRN (e.g., renal efferentnerves and the renal afferent nerves) reside within the adventitia layer4 that is surrounded by the fat layer 5. The adventitia layer 4 and thefat layer 5 exhibit properties that resemble that of a conductivematerial and properties that resemble that of a dielectric material. Assuch, microwave currents generated by an electromagnetic field in theadventitia layer 4 and the fat layer travel on the surface of each layer(conductive property) and travel through each layer (dielectricproperties). As such, losses in the adventitia layer 4 and the fat layer5 include conductive and dielectric losses.

In some embodiments, as illustrated in FIG. 5, the adventitia layer 4may be viewed as being analogous to a lossy dielectric film (LDF) formedon an inner surface of a coaxial cable outer conductor 24 (e.g., formedon an inner surface of the fat layer 5). High energy absorption ratescan therefore target the adventitia layer 4 and damage the nervescontained therewithin and/or adjacent thereto. Due to the rate of bloodflow through the renal artery RA, the microwave thermal energy that mayinduce tissue damage may be tempered in the body structure (e.g., renalartery RA) thereby resulting in the preservation of the intima layer 2and smooth muscle layer 3 and maintaining a viable arterial structure.

FIG. 6A illustrates a block diagram of the catheter hub 18 in accordancewith some embodiments of the present disclosure. The catheter hub 18 mayinclude five-ports and may be disposed at a proximal end of amulti-lumen tube 630, as illustrated in FIG. 6B. Catheter hub 18 mayinclude connectors to facilitate operable coupling of the five lumenswith corresponding elements of the generator, coolant source and return,and so forth. Catheter hub 18 is disposed at a proximal end of theflexible microwave catheter 30 and configured to enable the operablecoupling of various systems that may connect to the flexible microwavecatheter 30. The catheter hub 18 connects to a transmission line 14 andreceives denervating energy, generated by a source of denervation energy(e.g., a microwave generator 22), therefrom. The catheter hub 18 mayconnect to a fluid cooling system 40 and may provide an exchange ofcooling fluid between the flexible microwave catheter 30 and the fluidcooling system 40. The fluid cooling system 40 provides a source ofcoolant to the inflow conduit 42, receives coolant evacuated from thecatheter hub 18 through an outflow conduit 43, and deposits theevacuated coolant to a receiving destination (e.g., a receptacle,reservoir, or drain). The catheter hub 18 may connect to a guide wire 47for guiding and positioning the flexible microwave catheter 30. Thecatheter hub 18 may also connect to one or more sensor leads 34 a thatoperably couple one or more sensors 1534 (see FIG. 15A) on the flexiblemicrowave catheter 30 to a control system or sensor monitoring systemhoused in the microwave generator 22.

As illustrated in FIG. 6B, the flexible microwave catheter 30 inaccordance with the present disclosure includes a multi-lumen tube 630having a multi-port catheter hub 18 at a proximal end thereof (see FIG.2). The multi-lumen tube 630 has a generally elongated cylindrical outersurface having formed therein a plurality of conduits, passagewaysand/or lumens disposed longitudinally therein. The multi-lumen tube 630may be formed by any suitable manner of manufacture, such as withoutlimitation, extrusion. The multi-lumen tube 630 may include a centrallumen (e.g., flexible coaxial cable lumen 32 a) having a generallycircular cross-section extending axially therethrough and dimensioned toaccommodate a flexible coaxial feedline 32 (see FIG. 2). A first pair oflumens (e.g., guide wire tracking lumen 30 b and sensor lead lumen 30 c)having a generally a circular cross-section may be positioned onopposing sides of the central lumen (e.g., at a 12 o'clock and 6 o'clockposition) that are adapted to accommodate, e.g., a guidewire 47 and asensor conductor 34 a (see FIG. 8A), respectively. A second pair oflumens (e.g., inflow fluid passageway 44 a and outflow fluid passageway44 b) having a generally arcuate cross-section may be positioned onopposing sides of the central lumen, between the first pair of lumens(e.g., at 9 o'clock and 3 o'clock, respectively), to accommodate coolantinflow and coolant outflow, respectively.

The outer sheath 35 of the flexible microwave catheter 30 may includebraiding and/or windings to improve strength, to resist kinking, and/orto provide flexibility while maintaining sufficient stiffness. Outersheath 35 may include one or more steering wires (not shown) tofacilitate steering and manipulation of the flexible microwave catheter30 to a desirable position. Outer sheath 35 may include a dielectriccoating, such as, for example, Parylene, on the outer surface 35 c ofthe outer lumen to reduce blood clotting

As illustrated in FIG. 7, in some embodiments the flexible coaxial cable32 and at least part of the radiating portion are housed in the outersheath 35 of the flexible microwave catheter 30. Catheter hub 18includes an actuator 15 housed in the catheter hub 18 and coupled to theradiating portion 100. Actuator 15 is configured to deploy the radiatingportion 100 and cap 33 distally from the outer sheath 35, as discussedin detail hereinbelow.

The catheter hub 18 includes a coupler 45 or an adjustable fluid coupler845 as illustrated in FIGS. 8A-8B and FIG. 8C, respectively. Coupler 45and adjustable fluid coupler 845 provide connections to the one or morelumens 30 a-30 c, 44 a and 44 b formed in the flexible microwavecatheter 30 FIG. 8A illustrates a cross-section of a coupler 45 thatprovides connections to a flexible coaxial cable lumen 30 a, a guidewire tracking lumen 30 b and a sensor lead lumen 30 c. FIG. 8Billustrates a cross-section of a coupler 45 that provides connections toa flexible coaxial cable lumen 30 a and inflow and outflow fluidpassageways 44 a, 44 b. FIG. 8C illustrates an adjustable coupler 845that provides adjustable connections to a flexible coaxial cable lumen30 a and inflow and outflow fluid passageways 44 a, 44 b. Catheter hub18 and coupler 45 and adjustable coupler 845 may include any number andcombinations of lumens, pathways and electrical conduits required tofacilitate the various connections to the flexible microwave catheter30.

In FIG. 8A, a guide wire 47 is introduced into the guide wire trackinglumen 30 b through an opening (not shown) formed between the couplerbody 45 a and the proximal stain relief 45 c and one or more sensorleads 34 a are introduced into the sensor lead lumen 30 c throughanother opening formed between the coupler body 45 a and the proximalstrain relief 45 c.

In FIG. 8B, an inflow conduit 42 connects to inflow port 42 a andprovides cooling fluid to inflow plenum 42 b. Cooling fluid in inflowplenum 42 b flows distally through the inflow fluid passageway 44 aproviding cooling to the distal end of the flexible microwave catheter30. Inflow fluid passageway 44 a is in fluid communication with outflowfluid passageway 44 b of the distal end of the flexible microwavecatheter 30 (see FIGS. 15A-15B) such that cooling fluid travelsproximally through the outflow fluid passageway 44 b to the outflowplenum 43 b of the outflow port 43 a. Outflow conduit 43 connects theoutflow port 43 a and returns cooling fluid to fluid cooling system 40.Inflow port 43 a and outflow port 43 a are formed in the coupler 45between the coupler body 45 a and the proximal strain relief 45 calthough connections to any one or more of the lumens of the flexiblemicrowave catheter 30 (e.g. flexible coaxial cable lumen 30 a, guidewire tracking lumen 30 b, sensor lead lumen 30 c, inflow fluidpassageway 44 a and outflow fluid passageway 44 b) may be formed in anyportion of the coupler 45.

In some embodiments, catheter hub 18 includes an adjustable fluidcoupler 845, as illustrated in FIG. 8C. Adjustable fluid coupler 845includes a fluid coupler body 845 a forming an inflow plenum 842 b andan outflow plenum 843 b within the fluid coupler body 845 a. The inflowplenum 842 b is in fluid communication with the inflow conduit 842 andthe outflow plenum 843 b in fluid communication with the outflow conduit843.

Adjustable fluid coupler 845 may also include a distal and/or proximalstrain relief (not explicitly shown) that supports the flexiblemicrowave catheter 30 (e.g., the assemblage and connections to theflexible coaxial cable 32) and the transmission line 14. Additionalstrain reliefs may be provided to support the inflow conduit 41 a, theoutflow conduit 41 b and other elements that connect to the coupler 45and adjustable fluid coupler 845 described herein.

Adjustable fluid coupler 845 is configured to adjustably couple acoaxial cable (e.g., transmission line 14 or the coaxial flexible cable32), the fluid cooling system 30 and the outer sheath 35 of the flexiblemicrowave catheter 30. Fluid coupler body 845 a houses a fluid sealingsystem 819 and forms an outer sheath coupler 845 b on the distal end.Fluid sealing system 819 includes a distal sealing diaphragm 819 a, aproximal sealing diaphragm 819 b and a bypass bulb 819 c on the proximalend of the fluid coupler body 845 a. The distal sealing diaphragm 819 aand proximal sealing diaphragm 819 b may each include one or moreo-rings.

When discussing deployment herein, two approaches may be utilized. Inthe first approach, the distal end of the flexible microwave catheter 30is placed proximal the targeted tissue and the radiating portion 100 iseased out distally from the outer sheath 35 of the flexible microwavecatheter 30 (see at least FIGS. 42-44). In a second approach, the distalend of the flexible microwave catheter 30 is placed adjacent thetargeted tissue and the outer sheath 35 is pulled back proximallythereby deploying the radiating portion 100 (see at least FIGS.18B-18G).

The distal sealing diaphragm 819 a is disposed between a fluid flowlumen 37 and the interior surface of the fluid coupler body 845 athereby forming an outflow plenum 843 b between the distal inner surfaceof the fluid coupler body 845 a, the outer surface of the fluid flowlumen 37, the distal sealing diaphragm 819 a and the outer sheathcoupler 845 b. The outflow plenum 843 b receives fluid circulatedthrough the flexible microwave catheter 30 and provides the circulatedfluid to the outflow port 843 a.

Proximal sealing diaphragm 819 b is disposed between the fluid couplerbody 845 a and the flexible coaxial cable 32 thereby forming an inflowplenum 842 b between the inner surface of the fluid coupler body 845 a,the outer surface of the flexible coaxial cable 832, the distal sealingdiaphragm 819 a and the proximal sealing diaphragm 819 b. The inflowplenum 842 b receives cooling fluid from the inflow port 842 a. Thecooling fluid provided to the inflow plenum 842 b from the inflow port842 a flows through the flexible microwave catheter 30 in an inflowfluid passageway 44 a formed between the outer surface of the flexiblecoaxial cable 32 and the inner surface of the fluid flow lumen 37.

Bypass bulb 819 c provides a secondary seal between the fluid couplerbody 845 a and the flexible coaxial cable 32. Bypass bulb 819 c isconfigured to catch fluid which may pass through the proximal sealingdiaphragm 819 b. Bypass bulb 819 c may also provide strain relief to theflexible coaxial cable 32 that extends into and through the fluidcoupler body 845 a.

During use, coolant flows through the inflow port 842 a and into theinflow plenum 842 b. Fluid pressure in the inflow plenum 842 b forcesthe coolant into the inflow fluid passageway 844 a formed between theouter surface of the flexible coaxial cable 32 and the inner surface ofthe fluid flow lumen 37. Coolant continues to the distal end of theflexible microwave catheter 30, through the assembly (e.g., radiatingportion 100) on the distal end thereof, and into an outflow fluidpassageway 44 b. The outflow fluid passageway 44 b is formed between theouter surface of the fluid flow lumen 37 and the inner surface of theouter sheath 35. Fluid from the outflow fluid passageway 44 b isdeposited in the outflow plenum 843 a, flows through the outflow port843 a and to a coolant destination (e.g., storage container for re-useand/or drainage system).

The fluid flow lumen 37 is positioned coaxially around the flexiblecoaxial cable 32, and the outer sheath 35 is positioned coaxially aroundthe fluid flow lumen 37. A clearance between the outer diameter of theflexible coaxial cable 32 and inner diameter of the fluid flow lumen 37defines a first fluid conduit (e.g., inflow fluid passageway 44 a). Aclearance between the outer diameter of the fluid flow lumen 37 and aninner diameter of the outer sheath 35 defines a second fluid conduit(e.g., outflow fluid passageway 44 b. During use, a coolant, e.g.,carbon dioxide, air, saline, water, or other coolant media, may includea desirable dielectric property and may be supplied to the flexiblemicrowave catheter 30 and/or radiation portion 100 on the distal endthereof by one coolant conduit, and evacuated from the flexiblemicrowave catheter 30 by the other coolant conduit. That is, in someembodiments, the first fluid conduit (e.g., inflow fluid passageway 44a) supplies coolant and the second fluid conduit (e.g., outflow fluidpassageway 44 b) evacuates coolant. In other embodiments, the directionof fluid flow may be opposite. One or more longitudinally-oriented finsor struts (not explicitly shown) may be positioned within the inflowfluid passageway 44 a, the outflow fluid passageway 44 b and/or theouter sheath 35 to achieve and maintain coaxial centering among theouter sheath 35, fluid flow lumen 37, and/or the flexible coaxial cable32.

In some embodiments, actuator arm 15 b provides a linkage between theflexible coaxial cable 32 and the actuator 15. Actuator 15 and actuatorarm 15 b are configured to impart movement of the flexible coaxial cable32 through the adjustable fluid coupler 845. Movement of the flexiblecoaxial cable 32 deploys the radiating portion 100 as discussed indetail hereinbelow. During movement of the flexible coaxial cable 32, afluid-tight seal is maintained about the flexible coaxial cable by theproximal sealing diaphragm 819 b.

In some embodiments, coupler actuator arm 15 c provides a linkagebetween the adjustable fluid coupler 845 and the actuator 15. Actuator15 and coupler actuator arm 15 c are configured to impart movement tothe adjustable fluid coupler 845, which, in turn, imparts movement tothe inflow lumen 837 and outer sheath 35 about the flexible coaxialcable 32 which is fixed in position within the hub 18. As such, in someembodiments, the flexible coaxial cable 32 is moved longitudinallythrough the stationary adjustable fluid coupler 845, thereby deploying adistally-positioned radiating portion 100. In some embodiments, theflexible coaxial cable 32 is stationary and the adjustable fluid coupler845, outer sheath 35 and fluid flow lumen 37 are moved longitudinallyabout the flexible coaxial cable 32 thereby retracting the outer sheath35 from the distally positioned radiation portion 100.

In use, the flexible microwave catheter 30 is fed through a lumen to atarget tissue adjacent a natural body lumen and/or body structure. Incertain instances, the vascular system presents a serpentine routethrough the body to various natural body lumens and/or body structures.For example, the femoral artery provides access to the renal artery. Thevarious elements that form the flexible microwave catheter 30 may besubject to shifting and/or displacement forces arising from thediffering radii of the flexible microwave catheter 30 elements, whichcan cause undesirable effects such as kinking, twisting, etc.Advantageously, the various components that form the flexible microwavecatheter 30 and the connections to the fluid sealing system 819 areformed from material having resilient and lubricious qualities, thatenables the elements to move independently longitudinally (e.g.,proximally and/or distally) within the fluid coupler body 845 a and/orthe catheter hub 18. In this manner, the elements can shift in positionas the flexible microwave catheter 30 is guided into place while thefluidic integrity of the cooling elements are maintained.

The disclosed flexible microwave catheter 30 may be percutaneouslyintroduced into the femoral artery and positioned within the renalartery adjacent to the renal nerve bundle. Placement of the flexiblemicrowave catheter 30 may be intravascularly introduced and positionedadjacent to any desired target tissue. The configurable length microwaveenergy radiating device 100 includes a radiating portion that cooperatesadvantageously with the renal artery physiology to deliver denervationenergy to the renal nerve bundle while minimizing collateral damage tothe arterial vessel and related anatomical structures.

A catheter system in accordance with the present disclosure may includea guidewire having a knob or ball disposed at a distal end thereof. Theknob or ball may be radiopaque to enable positioning of the guidewire,and more particularly, the distal end thereof, using imaging(fluoroscopy, MRI, etc.). During use, a distal end of the guidewire maybe introduced into a body lumen and advanced into position, optionallyusing imaging as described above. A proximal end of the guidewire maythen be inserted into a corresponding port on the catheter that is incommunication with the guidewire lumen. The catheter is then advancedinto the body lumen to the desired location. As the catheter is advancedto the desired location, an indentation or other feature of the knob,ball, and/or catheter provides tactile feedback and/or a positive stopto facilitate correct positioning of the catheter.

In some embodiments, the distal end of the guide wire tracking lumen 30b terminates proximal from the radiating portion 100, as illustrated inFIGS. 9A-9C. Distal end 30 bd of guide wire tracking lumen 30 b forms aguide wire ball receiver 47 b in the outer sheath 35 of the flexiblemicrowave catheter 30. Guide wire ball receiver 47 b is configured toreceive the proximal end of guide wire 47 as illustrated in FIG. 9A.

In use, guide wire 47 and distal guide wire ball 47 a are inserted intothe body, and distal guide wire ball 47 a is positioned adjacent totargeted tissue using a guidance system (e.g., imaging system or anysuitable guidance and positioning system). After positioning the distalguide wire ball 47 a at a desired location, the proximal end (notexplicitly shown) of the guide wire 47 is inserted into the guide wireball receiver 47 b, passed through the guide wire tracking lumen 30 band through the catheter hub 18 (see FIGS. 2, 6A, and 7B).

Flexible microwave catheter 30 is guided to the target tissue via theguide wire 47. As illustrated in FIGS. 9B and 9C, distal guide wire ball47 a is received by the guide wire ball receiver 47 b such that theguide wire ball 47 a is proximal to the radiating portion 100.

Some embodiments and structures discussed herein follow the coaxialstructure analogy described hereinabove and illustrated in FIGS. 4A-4Cand 5 wherein the coaxial structure incorporates one or more layers of anatural body lumen to form a coaxial feedline structure. Like any othercoaxial structure, the coaxial-positioning of structures that form thewaveguide are directly related to the operation and/or efficiency of thewaveguide.

FIGS. 10A-12A each illustrate a flexible microwave catheter 30positioned in a renal artery RA and FIGS. 10B-12B illustrate therespective cross-section thereof. In FIGS. 10A and 10B, the flexiblemicrowave catheter 30 and distal radiating portion 100 are centered inthe renal artery RA. In FIGS. 11A and 11B, the flexible microwavecatheter 30 and distal radiating portion 100 are offset from dead centerby 0.5 mm and in FIGS. 12A and 12B, the flexible microwave catheter 30and distal radiating portion 100 are offset from dead center by 1 mm.Each of FIGS. 10A-12A and 10B-12B illustrate a distribution of thermalenergy in and around the renal artery from the application of 25 W ofmicrowave energy to the flexible microwave catheter 30 for about 2minutes.

In each of FIGS. 10A-12A, the flexible microwave catheter 30 includes afirst proximal waveguide, formed by the flexible coaxial cable 32, and asecond distal waveguide, formed by the inner conductor 20 and a portionof the anatomical structure. The flexible coaxial cable 32 that formsthe first proximal waveguide includes an inner conductor 20 centered andcoaxially offset from an outer conductor 24 by a dielectric layer 22.The second distal waveguide is an anatomical resonant structure 1032,1132, and 1232 that includes a portion of the inner conductor 1020,1120, 1220, respectively, extending distally from the flexible coaxialcable 32, a portion of the renal artery RA coaxially offset from theinner conductor by a transitional dielectric 1026, 1126, 1226 and fluid1 contained in the renal artery.

A radiating portion 100 of the flexible microwave catheter 30 is formedat a distal end of the flexible coaxial cable 32. In embodimentsaccording to the present disclosure, and of a manufacturing processtherefor, a portion of the outer conductor 24 is removed to expose theinner conductor 20 thereby forming a feed gap 1050, 1150, 1250 (e.g.,feed point) that facilitates the propagation of denervation energy, suchas microwave energy. Optionally or alternatively, a transitionaldielectric 26 is disposed in the feed gap 1050, 1150, 1250. Thetransitional dielectric 1026, 1126, 1226 corresponds generally and/orgeometrically to the portion of the outer conductor 24 removedtherefrom.

The transitional dielectric 26 may have dielectric properties betweenthat of the inner dielectric 22 and that of the expected or averagedielectric properties of the targeted anatomical structures (e.g., therenal artery RA, body lumen and/or other body structure). Use of atransitional dielectric 26 in this manner may improve coupling betweenthe radiating portion 100 and the targeted tissue, by, e.g., reducingreflections, reducing standing waves (e.g., VSWR), and by providingimpedance matching between the radiating portion 100 and targetedtissue.

In FIGS. 10A and 10B, the inner conductor 20 is coaxially centered inthe renal artery RA. As such, the anatomical resonant structure 1032 issubstantially coaxial thereby generating a substantially balancedresonating structure. The balanced anatomical resonant structure 1032generates heating, due to dielectric losses and/or conductive losses, inthe anatomical portions of the renal artery structure (e.g., one or morelayers of the renal artery as discussed hereinabove). As illustrated inFIG. 10B, centering of the inner conductor 20 within the renal artery RAgenerates substantially uniform heating 1000 a about the renal arteryRA.

Centering the inner conductor 1020 in the renal artery RA, in additionto forming a balanced anatomical resonant structure 1032, generatessubstantially uniform heating 1000 a and even distribution of thegenerated thermal energy about the renal artery RA. Additionally,heating of the distal end of the flexible coaxial cable 32 and heatingof the exposed inner conductor 1020 in the anatomical resonant structure1032 are maintained to acceptable temperatures.

As illustrated in FIGS. 11A-12A, offsetting the inner conductor 20, asillustrated in FIGS. 11A-12A and 11B-12B, with respect to the anatomicalstructure (e.g., the renal artery RA) that forms the anatomical resonantstructure 1132 and 1232 results in the generation of non-uniform heating1100 a, 1200 a about the renal artery RA.

In FIGS. 11A and 11B, the inner conductor 20 is offset from the centerof the renal artery RA by 0.5 mm and in FIGS. 12A and 12B the innerconductor 20 is offset from the center of the renal artery RA by 1 mm,in each instance an unbalanced anatomical resonant structure 1132 and1232 is formed. The unbalanced anatomical resonant structure 1132, 1232generates non-uniformed heating 1100 a, 1200 a about the renal artery RAforming a hot-spot adjacent the renal artery RA. The hot-spot may resultin raising the temperatures of the portion of the renal artery RAadjacent the hot spot and may result in irreversible tissue damage.Additionally, offsetting the inner conductor 20 may also heat the distalend of the flexible coaxial cable 32 and/or a portion of the exposedinner conductor 20 to unacceptable temperatures.

As illustrated in FIGS. 10A-12A, each anatomical resonant structure1032, 1132, 1232 generates a large delta between the inside temperatureand the outside temperature of the renal artery RA. FIG. 13 illustratesexperimental data showing the temperature inside and outside of therenal artery RA plotted against the power measured at the beginning ofthe flexible coaxial cable 32 (see FIG. 7). The linear representation ofthe maximum temperature inside the renal artery 1334 a and the linearrepresentation of the maximum temperature outside the renal artery 1334b demonstrates that the anatomical resonant structures 1032, 1132, 1232generate temperatures outside of the renal artery RA that will achieve acytotoxic temperature (e.g., a quality of thermal energy toxic to cells)in the outer layers of the vessel while maintaining less than lethaltemperatures inside the renal artery RA.

As discussed hereinbelow, the flexible microwave catheter 20 may includea centering device configured to coaxially center the radiating portion100 in a natural body lumen or in a natural body structure therebyforming a balanced anatomical resonant structure as discussedhereinabove. Centering device described herein includes stent-likeexpandable members (see FIGS. 16A-16C, 17A-17B, 18A, 19A, 20, 21 and22A-22B), balloon-like inflatable members (see FIGS. 24, 25 a-25B,26A-26C and 58A-58D), compressible expandable members (see FIGS.27A-35), repositionable expandable members (see FIG. 18A), a centeringdevice with a plurality of members (see FIGS. 32A-32B, 35, 37A-37B,39A-39B, 40A-41B), two or more fin expandable members (see FIGS. 27A-27Dand 28), expandable basket members (see FIGS. 29-35), clover leafexpandable members (see FIG. 34-35), expandable single and double paddlemembers (see FIGS. 36A-39B), expandable single and double propellermembers (see FIG. 36A-39B), expandable tines (see FIGS. 40A-40B),expandable fin members and expandable helical fin members (see FIG.41A-41B), and any combination thereof.

The centering structures described herein provide minimal resistance toblood flow along the structure, which enables the flowing blood to coolthe structure and tissues not targeted for ablation.

In some embodiments, the centering device (or devices) are restrained inan outer sheath and self-deploy (e.g., expand), and thereby center theradiation portion 100, when released from the outer sheath. Similarly,the centering device self-retracts when retracted into the outer sheath.

Centering structures described herein may be formed from conductivematerials, non-conductive materials, dielectric materials or anycombination thereof. In some embodiments, a conductive centeringstructure includes a shaped memory material such as, for example, anickel-titanium alloy (e.g., nitinol), or a ferromagnetic shape-memoryalloy.

In some embodiments, a non-conductive centering structure includes ashaped-memory polymer. The shaped-memory polymer may be triggered toexpand to a shape-memory position by an electromagnetic field generatedby the delivery of microwave energy. As such, the centering devicecenters the radiating portion 100 within the body lumen while theradiating portion 100 delivers microwave energy.

In some embodiments, the centering device may be used to anchor theradiating portion of the flexible medical catheter into tissue oradjacent targeted tissue. Alternatively, the centering device may beself-centering via fluid/hydrodynamic, and/or mechanical forces withinthe body lumen BL.

In some embodiments, centering devices may also be configured todielectrically buffer the microwave currents from the surroundingphysiology.

Embodiments and features described herein may be selected and combinedwith other embodiments and features described herein in any combination.For example, radiating portion may be selected from a radiating portionwith a monopole antenna (see FIG. 5), one or more slotted feed gaps (seeFIGS. 10A-12A, 14F, 16A-C, 19A-F, 20-22B, 50-53, 55 and 57), a dipoleantenna (see FIG. 17A), a radiating portion with a helical fed gap (seeFIGS. 42-45, 47, 54, 56 and 57), or any combination thereof. Theselected radiating portion may be combined with a fluid cooled flexiblemicrowave catheter that connects and combined with a catheter with afluid coupler or a adjustable fluid coupler for deploying the radiatingportion from the outer sheath of the flexible microwave catheter.Further, any of the above named combinations may include a centeringdevice or structure. The centering device or structure may connect tothe catheter hub that facilitates the actuation and/or deployment of thecentering device.

Centering devices may provide additional functionality in addition topositioning the device. For example, in some embodiments the centeringdevice may form a choke or balun that defines and/or limits thederivation region and/or defines and/or limits the anatomical resonantstructure. In some embodiments, the centering device may include one ormore structures wherein the structure(s) defines a pattern of applieddenervation energy.

One embodiment of a radiating portion 100 according to the presentdisclosure, and of a manufacturing process therefor, is illustrated inFIGS. 14A-14E. In the first step of the manufacturing process, aflexible coaxial cable 32 is provided as illustrated in FIG. 14A. Acylindrical or semi-cylindrical portion of the outer conductor 1424 anddielectric 1422 is removed to expose the inner conductor thereby forminga feed gap 1450 (e.g., feedpoint). Feed gap 1450 facilitates thepropagation of denervation energy, such as microwave energy.

The portion of the outer conductor 1424 may be removed by etching,cutting, or stripping the outer conductor off the cable in a ring withlength of approximately 0.01″ leaving approximately ¼ wavelength ofcoaxial cable distal to this location.

Optionally, a transitional dielectric 1426 may be disposed in the feedgap 1450, corresponding generally to the cylindrical section of theouter conductor 1424 that is removed, as illustrated in FIG. 14B. Thetransitional dielectric 1426 has dielectric properties between that ofthe inner dielectric 1422, and that of the expected or averagedielectric properties of the anatomical structures with which theantenna is to be used, e.g., the renal artery and/or blood in the renalartery. Transitional dialectic 1426 may be a formed from any suitabledielectric material and/or dielectric fluid. Use of a transitionaldielectric 1426 in this manner may improve coupling between theradiating portion 100 and targeted tissue, by, e.g., reducingreflections, reducing standing waves (e.g., VSWR), and by providingimpedance matching between the radiating portion 100 and tissue.

As further illustrated in FIG. 14B, a distal-most end of the flexiblecoaxial cable 32, a portion of the outer conductor 1424 and innerdielectric 1422 are removed thus exposing a portion of the innerconductor 1420. As illustrated in FIG. 14C, a short conductive (e.g.,metallic) cylinder, disc, or cap 1433 having an opening defined at thecenter thereof, the opening being dimensioned to accept the innerconductor 1420, is joined at the opening to the exposed end of the innerconductor 1420 and at the perimeter thereof to the outer conductor 1424.This distal “cap” 1433 shorts the inner conductor 1420 to the outerconductor 1424, which, in turn, may optimize, control, focus, and/ordirect the general distal radiating pattern of the radiating portion100, e.g., reduce, focus, shape and/or enhance the propagation ofdenervation energy beyond the distal end of the radiating portion 100.

In some embodiments, cap 1433 is formed from a high-temperaturedielectric such as a plastic, ceramic, or other suitable dielectricmaterial. Cap 1433 may include a high-temperature dielectric and aconductive portion formed therein that provides a short or low impedancepath between the inner conductor 1420 and the outer conductor 1424. Insome embodiments, the distal portion of the cap 1433 is formed from anon-conducting material, such as, for example, a polymer.

In some embodiments, a choke or balun 1408 short may be fixed to theouter conductor 1424 at a position proximal of the feed gap 1450, asillustrated in FIG. 14D. The balun 1408 may include a short conductive(“metallic”) ring 1408 a having an inner diameter dimensioned to acceptthe outer conductor 1424. The balun ring 1408 a is electrically bonded(e.g., soldered, welded, and/or mechanically connected) to the outerconductor 1424. The balun ring 1408 a is positioned a distance from thefeed gap 1450 of about 180 degrees in phase length. This balun ring 1408a affects a microwave short which, in turn, may optimize, control,focus, and/or direct the general radiating pattern of the radiatingportion 100, e.g., reduce the propagation of denervation energy beyondthe proximal end of the radiating portion 100 and/or the balun 1408.Balun ring 1408 a may improve impedance matching, reduce reflectionsand/or standing waves, improve efficiency, and reduce the risk ofembolism (e.g., clotting).

The balun 1408 may further include a balun dielectric sleeve 1408 b,which may be formed from extruded polytetrafluoroethylene (PTFE, e.g.,Teflon®), from extruded polyethylene terephthalate (PET) and/or fromextruded fluorinated ethylene propylene (FEP). The balun dielectricsleeve 1408 b may be positioned over the radiating portion 100 of theassembly and mated to the balun ring 1408 a. The balun dielectric sleeve1408 b may further include a length of heat shrink tubing 1408 c, havinga conductive material on a surface thereof, preferably an inner surface,that may be positioned over the PTFE balun dielectric sleeve 1408 c tochange a dielectric property and/or to improve the performance of thebalun 1408 and thus, improve the radiating pattern of denervationenergy. A silver ink may be disposed on the inner surface of the heatshrink tubing 1408 c, whereupon shrinking the heat shrink 1408 c overthe balun ring 1408 a and balun dielectric 1408 b forms a resonantmicrowave structure that improves the performance of the balun 1408 and,in turn, improves the radiating pattern of the denervation energy.

In some embodiments, the balun dielectric sleeve 1408 b and metal ring1408 a are then covered from the proximal end to near the distal endwith a heat shrink coated in conductive ink (e.g., a balun outerconductor). In some embodiments, the distal end of the balun dielectricsleeve 1408 b is not coated with the conductive heat shrink, and thusforms a balun extended dielectric that improves balun performance.

As illustrated in FIGS. 15A-15B, the cap 1533 connects to the distal endof the flexible coaxial cable 1532, the distal end of the fluid flowlumen 1537 and the distal end of the outer sheath 1535. A distal end ofthe fluid flow lumen 37 is sealably joined to the proximal face of thecap 1533 to achieve and maintain concentric alignment among theradiating portion 100 elements. One or more cap coolant passageways 1533a, 1533 b formed within the cap 1533 enables coolant to circulate fromthe inflow fluid passageway 1544 a to the outflow fluid passageway 1544b, which facilitates the flow of coolant through the radiating portion100, and may advantageously provide cooling of the radiating portion 100and cap 1533.

Cap 1533 may receive the inner conductor 1520 via the proximal innerconductor receiver 1533 c and connect to the outer conductor 1524thereby providing a short or low resistance connection between the innerconductor 1520 and the outer conductor 1524.

Cap 1533 connects to outer sheath 1535 and forms a fluid-tight sealtherebetween. Cap 1533 may be bonded to the outer sheath 1535 bywelding, bonding, adhesive, or any other suitable manner of connection.Cooling fluid enters cap fluid chamber 1533 d through cap inflow coolantpassageways 1533 a and flows out of the cap fluid chamber 1533 d throughcap outflow coolant passageways 1533 b.

A temperature sensor 1534 may be operatively associated with theradiating portion 100 and/or cap 1533 in accordance with the presentdisclosure. For example, and without limitation, one or morethermoprobes, pressure sensors, flow sensors, or any other suitablesensor may be included within the radiating portion 100, cap 1533, outersheath 1535, the flexible coaxial cable 1532, the inflow and/or outflowfluid passageway 1544 a, 1544 b, a cap fluid chamber 1533 d or any otherconduit and/or structure (e.g., a mesh, balloon, expandable and/ordeployable member,) described herein. In some embodiments, temperaturesensor 1534 may be positioned on the distal end of the cap 1533. One ormore thermoprobes may be included within the flexible microwave catheter1530 (e.g., outer sheath, flexible coaxial cable 32, one or more fluidchambers or conduits, outer dielectric insulating layer 128, shieldingouter conductor 124 a, and/or any other structure described herein).

Temperature sensor 1534 may be positioned distal to the active heatingzone of the radiating portion 100. The microwave energy delivery system12 thereby monitors the temperature of the fluid passing through thehottest location. If the temperature sensor 1534 measures a temperatureabove a clotting temperature threshold, the system 12 may temporarily orpermanently halt power delivery. In some embodiments, one or moretemperature sensors 1534 may be positioned at the discharge of a fluidpassageway formed in, thorough, or around a centering device asdiscussed hereinbelow.

In some embodiments, cap 1533 or any portion of the distal tip of theflexible microwave catheter 30 may include a radiopaque material (suchas barium) to enhance the visibility thereof during fluoroscopy.

As discussed hereinabove with respect to FIGS. 6A and 8A-8C, a catheterhub 18 at a proximal end of the flexible microwave catheter 30 enablesthe operable coupling of a source of denervating energy (e.g., amicrowave generator 22) to the flexible coaxial cable 32, a fluidcooling system 19 to the inflow fluid passageway 44 a, and a receivingdestination (e.g., a receptacle, reservoir, or drain) for coolantevacuated from the outflow fluid passageway 44 b.

As illustrated in FIGS. 16A-16C, a flexible microwave catheter 1630 inaccordance with the present disclosure may include one or morestent-like expandable elements 1670 associated with the radiatingportion 100. As illustrated in FIG. 16A, the stent-like expandableelements may be maintained in a compressed state while guiding theflexible microwave catheter 1630 through the vascular system to aposition adjacent the target tissue. In some embodiment, the stent-likeexpandable element 1670 is maintained in a compressed state by thedistal portion of the outer sheath 1635. In other embodiments, thestent-like expandable element 1670 is stowed in a compressed statewithin the outer sheath 1635.

During use, and as illustrated in FIG. 16B, the outer sheath 1635 may beretracted proximally and/or the stent-like expandable element 1670 maybe advanced distally, causing the stent-like expandable element 1670 toextend from the confines of the outer sheath 1635 and to expand into agenerally tubular, cylindrical and/or balloon-like shape around theradiating portion 100 thereby centering the radiating portion 100 of theflexible microwave catheter 1630 within the lumen (not specificallyshown). The stent-like expandable element 1670 may be positioned suchthat the center of the stent-like expandable element 1670 is generallycoincident with a feedpoint (e.g., feed gap 1650) of the radiatingportion 100. Feed gap 1650, as illustrated in FIGS. 16A-16C, may includean exposed slotted portion of the inner conductor 1620 wherein a portionof the outer conductor 1624 has been removed. An exposed portion of theinner conductor 1620 may also include a transitional dielectric 1650that covers the inner conductor 1620.

At least a portion of the stent-like expandable element 1670 may bepositioned distal to the radiating portion 100, positioned proximally tothe radiating portion 100, may generally surround the radiating portion100, or any combination thereof. The stent-like expandable element 1670may be formed from, e.g., wire mesh, wire members, stamped metal, and/ormay be formed from any suitable electrically conductive material,including without limitation, stainless steel, copper, silver, platinum,gold, shape memory allow (e.g., Nitinol) and the like. In someembodiments, stent-like expandable element 1670 may also be formed from,and/or may include, a polymer or composite material with low electricalconductive such as a polyurethane, polyimide, FEP, PET, and/or PTFE.

FIG. 16C illustrates a stent-like expandable mesh element 1672. In someembodiments, the stent-like expandable mesh element 1672 includes adistal and a proximal end-cap mesh 1672 a joined by a tubular body mesh1672 b. At least a portion of the tubular body mesh 1672 b extendsradially outward from the radiating portion 100 including the feed gap1650 (e.g., inner conductor 1620 and transitional dielectric 1650).

In some embodiments, at least a portion of the endcap mesh 1672 aincludes a variable mesh density wherein the mesh density is greater atthe distal and/or proximal ends, and less dense along the length of thetubular body mesh 1672 b. The mesh structures described herein provideminimal impedance to blood flow distally along the structure, whichenables the flowing blood to cool structures and tissues not targetedfor ablation (blood, intima, and media of renal artery).

In some embodiments, the stent-like expandable element 1670 may be leftin place within the renal artery RA as a stent to reduce complicationsfrom a potential stenosis. The stent-like expandable element 1670 maydetach from the flexible microwave catheter 1630 after energyapplication and be left in place to mechanically support the renalartery RA.

In some embodiments, the stent-like expandable element 1670, or otherexpandable device described herein, may include three positions. In afirst position, the stent-like expandable element 1670 is fullyexpanded/extended for initial placement. In a second position, thestent-like expandable element 1670 is retracted proximally to allow fordeployment while maintaining the stent-like expandable element 1670 inplace about the radiating section 100. In a third position, thestent-like expandable element 1670 is fully retracted such that thefinal proximal portion of the stent-like expandable element 1670 isreleased. The far distal portion of the stent-like expandable element1670 may be released from the flexible microwave catheter 30 when thecatheter 30 is pulled proximally out the renal artery RA. For example,it may fit into a slot which faces in the distal direction and thereforehold the mesh when the catheter is advanced distally, but releases onlywhen the device is pulled proximally and the sheath is fully retracted.

In FIGS. 16A-16C, cap 1633 connects to the distal end of the radiatingportion 100 and provides an electrical short between the inner conductor1620 and outer conductor 1624, 1624 a. Temperature sensor 1634 may behoused in the cap 1633 or housed in any other portion of the radiatingportion 100, stent-like expandable element 1670, stent-like expandablemesh element 1672, flexible coaxial cable 1632 or outer sheath 1635.

In some embodiments, the proximal and/or distal portion of thestent-like expandable element 1670 and/or the proximal and/or distalportion of the stent-like expandable mesh element 1672 a form a choke orbalun short. The choke or balun short substantially confines theelectromagnetic field to an electromagnetic boundary defined by thechoke or balun short. As such, thermal heat generation is substantiallylimited to the portion radially outward from the feed gap.

In some embodiments, the centering structure forms a Faraday cage thatis substantially opaque to microwave energy at the distal and proximalends while remaining substantially transparent to microwave energy alongat least a portion of the length thereof. Such an arrangement may haveadvantages, since it enables the device to target delivery ofdenervation energy radially (e.g., circumferentially to the renalartery) while reducing or eliminating the delivery of denervation energyaxially (e.g., distally and proximally along the renal artery). Aflexible medical catheter in accordance with the present disclosure mayimprove operative outcomes by enabling a surgeon to precisely deliverenergy to targeted tissue while reducing or eliminating complicationsarising from collateral tissue effects.

The mesh forming the proximal portion and distal portions of the Faradaycage may form a choke or balun short that confines a substantial portionof the anatomical resonant structure to the anatomical structuresbetween the proximal portion and distal portion of the Faraday cage.

In some embodiments, the mesh may be configured to accommodate specificwavelengths, or ranges of wavelengths, of denervation energy that may beutilized during denervation procedures. For example, and withoutlimitation, to provide the desired microwave radiation pattern the meshspacing (e.g., space between adjacent mesh elements) may be less thanabout 1/10λ (e.g., one-tenth the wavelength of the intended microwavesignal) at the distal and proximal ends of the mesh structure to createan effective microwave boundary. Along the length of the mesh, the meshspacing may be greater than about 1/10λ to avoid creating a microwaveboundary thereby allowing for radiation of denervation energy.

Advantageously, the open mesh structure of the disclosed device enablesblood to continue to flow along the surgical site during a denervationprocedure, thereby increasing the time window available to the surgeonfor completion of the procedure. Maintaining blood flow provides thermalmanagement of the flexible microwave catheter 30 and the radiatingportion 100, while providing cooling of the inner structure of thevessel walls.

Some embodiments according to the present disclosure include a radiatingportion having a plurality of feed gaps. The radiating portion of aflexible microwave catheter in accordance with the present disclosuremay include a mesh structure having a plurality of windows definedtherein. Windows may include one or more materials with properties thatare different than the body of the mesh structure. Alternatively, awindow may be an open structure characterized by the absence of material(e.g., an aperture). As discussed herein, a window in a structure formedfrom a different material and a window in a structure characterized bythe absence of material (e.g., an aperture) are used interchangeably.The material property may include a mechanical property, a materialproperty, an electrical property, or any combination thereof. The windowmaterial properties may include a mechanical difference such as, forexample, mesh spacing, mesh gauge, mesh formation, mesh thickness or anycombination thereof. The window material property may include a physicaldifference such as, for example, material type, composition, materialconstruction or any combination thereof. The window property may includean electrical difference such as, for example, conductivity, resistivityor any combination thereof.

The position of the windows may be distributed laterally along the meshstructure, and may be indexed radially and/or may be distributedradially. In some embodiments, three windowed slots are indexed radially60° apart and distributed longitudinally along the mesh structure. Thewindows correspond to defined treatment zones (e.g., kill zones) thatenable a surgeon to select with precision the tissue regions targetedfor denervation. A multi-window mesh structure, as describe herein, mayalso be utilized with a single feed gap design. A multi-window designmay have advantages in that during denervation only a portion of thevessel wall is subjected to energy delivery, while still ensuring therenal nerve bundle is treated effectively.

Mesh structures may be configured to center the radiating portion 100 ofthe flexible microwave catheter 30 in a body lumen and/or a bodystructure.

Mesh structures may include conductive materials, non-conductivematerials or a combination of conductive and non-conductive materials.Conductive mesh structures are configured to interact with the radiatingportion of the flexible microwave catheter. For example, a conductivemesh structure may form part of a resonance structure. In someembodiments, the conductive mesh structure forms part of an anatomicalresonant structure that includes at least a portion of the tissuesurrounding the mesh structure.

At least a portion of a mesh structure may include a conductive portionconfigured to form a microwave choke or balun. For example, a distaland/or proximal portion of the mesh structure may include a conductivemesh structure configured to shunt the microwave energy signal therebypreventing at least a portion of the microwave energy signal frompropagating proximally and/or distally of the conductive mesh structure.

In some embodiments, the stent-like expandable element 1670 is coupledto an actuator (e.g., actuator 15 and/or rotating actuator 15 g).Actuator may be configured to mechanically expand the stent-likeexpandable element 1670 (or configured to expand, deploy or open acentering device described herein). Distal or proximal end-cap mesh 1672a may be coupled to actuator 15 and expanded and/or contracted byvarying the position of the actuator 15.

Actuation of the centering device (e.g., stent-like expandable elementor other centering device described herein) may vary the amount of forceexerted to the inner surface of the body lumen thereby shaping theanatomy to a desirable structure and/or geometry. The body lumen may beshaped to form a particular shape, diameter and/or cylindrical structureto facilitate delivery of energy to the targeted tissue.

As illustrated in FIGS. 17A-17B, the conductive mesh structure 1772includes a plurality of windows 1773 a-1773 e defined in at least aportion of the lengthwise section. The conductive mesh structure 1772 isconfigured to enable the delivery of denervation energy to tissuethrough the windows 1773 a-1773 e, while attenuating or eliminating thedelivery of denervation energy to tissue from the remainder of the meshstructure 1772. Proximal and distal mesh end-caps 1772 a, 1772 b may beconfigured to substantially limit the resonant structure to the confinesof the mesh structure 1772.

In some embodiments, the conductive mesh structure 1772 has densitysufficient to limit radiation of microwave energy therethrough, exceptfor one or more of the windows 1773 a-1773 e where the structure has adensity of about zero. The clinical effect is therefore ablation of therenal artery in a pattern corresponding to the windows 1773 a-1773 e.

In some embodiments, the window region of the mesh 1772 may have a meshdensity of greater than about 1/10λ (e.g., mesh elements spaced greaterthan 1/10λ apart), while the non-window region of the mesh may have amesh density of less than about 1/10λ (e.g., mesh elements spaced lessthan 1/10λ apart). In some embodiments the window region of the mesh1772 includes a non-conductive material or any material that istransparent to microwave energy. In other embodiments, the windows 1773a-1773 e formed in conductive mesh structure 1772 are open and do notinclude any material what so ever.

During use, the flexible microwave catheter may be positioned adjacentto targeted tissue, the conductive mesh structure 1772 is then expanded,and an application of denervation energy is applied to tissue exposed tothe windows 1773 a-1773 e.

FIG. 17B illustrates a renal artery RA after the application ofdenervation energy by the device illustrated in FIG. 17A. Thedenervation energy applied to the renal artery RA through each of thewindows 1773 a-1773 e generates a corresponding denervation zone 1774a-1774 e.

For illustrative purposes, the renal artery RA in FIG. 17B is providedwith a plurality of renal nerves RN extending longitudinally along therenal artery RA. The denervation zones 1774 a-1774 e (and thecorresponding windows 1773 a-1773 e) are longitudinally spaced from eachother while providing circumferential overlap such that each of theindividual renal nerves RN pass through at least one of the denervationzones 1774 a-1774 d. By this arrangement, denervation energy is appliedto each of the renal nerves through at least one of the plurality ofwindows 1773 a-1773 e along the length of the renal artery RA.

Embodiments that provide circumferential overlap and/or circumferentialdelivery of energy may require a single treatment to obtain a desirableoutcome.

As illustrated in FIG. 18A, a conductive mesh structure 1872 includes awindow 1873 defined in at least a portion of the lengthwise sectionthereof. The conductive mesh structure 1872 is configured to enable thedelivery of denervation energy to tissue through the window 1873, whileattenuating or eliminating the delivery of denervation energy to tissuefrom the remainder of the mesh structure 1872. Proximal and distal meshend-caps 1872 a, 1872 b may be configured to substantially limit theresonant structure to the confines of the mesh structure 1872.

In some embodiments, the window 1873 may include a mesh which includes amesh density greater than about 1/10λ. The non-window region of theconductive mesh 1872 may have a mesh density of less than about 1/10λ.

A method of applying denervation energy, utilizing the conductive meshstructure 1872 illustrated in FIG. 18A, is illustrated in FIGS. 18B-18H.As illustrated in FIG. 18B, the distal end of the flexible microwavecatheter 1820 is positioned in a target artery (e.g., renal artery RA).As illustrated in FIG. 18C the outer sheath 1835 is retracted to removethe conductive mesh structure 1872 and the conductive mesh structure1872 is expanded. The window 1873 is directed to a first target portion1874 a of the renal artery RA and a first application of denervationenergy is applied to renal artery RA as first targeted tissue 1874 a isexposed to the window 1873. After the initial application of denervationenergy, the conductive mesh structure 1872 is repositioned, asillustrated in FIG. 18D, thereby exposing a different region (e.g.,second targeted tissue 1874 b) of the renal artery RA to the window1873. The conductive mesh structure 1872 may be fully or partiallycollapsed during repositioning and subsequently re-expanded asillustrated in FIG. 18E. After repositioning the flexible microwavecatheter 1820, a second application of denervation energy is applied tothe second target tissue 1874 b. As illustrated in FIGS. 18F-18G,subsequent repositions of the flexible microwave catheter 1830 andapplications of denervation energy may be delivered in this manner asneeded, thereby applying energy to a first, second, and third targettissue 1874 a-1874 c, and so forth.

The conductive mesh structure 1872 is initially positioned at adistal-most position within a body vessel, and drawn proximally for eachsubsequent repositioning. In some embodiments, the conductive meshstructure 1872 (and hence, the window 1873) is independently rotatableabout the longitudinal axis of the flexible microwave catheter 1830. Arotating actuator 15 g (see FIG. 7), such as without limitation, a knobor a lever, may be provided on the catheter hub 18 (see FIG. 7) toenable a surgeon to rotate and/or manipulate the conductive meshstructure 1872 in situ without the need to withdraw and re-insert theflexible microwave catheter, and/or without needing to rotate the entireflexible microwave catheter 1830.

The flexible microwave catheter 30 in FIGS. 18A-18H may include atemperature sensor 1834 at a distal end of the radiating portion 100.Temperature sensor 1834 may be used to measure the temperature of fluidcirculating through the renal artery and passing through the proximaland distal end-cap mesh 1872 a. The fluid temperature measured by thetemperature sensor 1834 may be indicative of the energy delivered by theradiating portion 100. The fluid temperature measured by the temperaturesensor 1834 may be indicative of the flow rate of fluid through theproximal and distal end-cap mesh 1872 a. A low flow rate may becharacterized by an unexpected rise in temperature, a change in the rateof temperature change, and/or the failure of a temperature decrease whenenergy delivery is terminated. Low flow rate may indicate the presenceof a clot, emboli, or other blockage proximal the conductive meshstructure 1872.

Sensor leads 1834 a are routed along the outer surface of the conductivemesh structure 1872. The conductive mesh structure 1872 at leastpartially isolates the sensor leads 1834 a from the electromagneticfield generated by the radiating portion 100.

One or more indicia may be provided in association with the rotatingactuator 15 g to apprise a surgeon of the position of the conductivemesh structure 1872. In some embodiments, the conductive mesh structure1872, or a portion thereof, is formed from material detectable byimaging techniques, thereby enabling a surgeon to determine the positionthereof by fluoroscopic and other medical imaging devices, e.g., MRIand/or angiography.

In some embodiments, the radiating portion 100 includes an antennastructure in accordance with the present disclosure that includes aplurality of feed gaps 1950 a, 1950 b, 1950 c (e.g., energy feedpoints).FIG. 19A illustrates a flexible microwave catheter 1930 including aflexible coaxial cable 1932 connected to a radiating portion 100 on thedistal end thereof with a plurality of radiating feed gaps 1950 a-1950c. Radiating portion 100 includes a first radiating feed gap 1950 a, asecond radiating feed gap 1950 b distal to the first radiating feed gap1950 a, and a third radiating feed gap 1950 c distal to the first andsecond radiating feed gaps 1950 a, 1950 b. In these embodiments, thetotal power delivered to tissue is divided among the plurality ofradiating feed gaps 1950 a-1950 c. A dimension of each feed gap 1950a-1950 c, e.g., the longitudinal length of the exposed inner conductor,may be tailored to determine which fraction of the energy total isdelivered by each respective feed gap 1950-1950 c.

FIG. 19A illustrates just one non-limiting example having a radiatingportion 100 with three radiating feed gaps 1950 a-1950 c. Since theenergy arriving from the generator initially reaches the first radiatingfeed gap 1950 a, the feed gap 1950 a may be dimensioned to deliverone-third of the arriving energy. Moving to the second radiating feedgap 1950 b, since one-third of the total energy was propagated by thefirst radiating feed gap 1950 a, a remainder of two-thirds of the totalenergy arrives at the second radiating feed gap 1950 b. Accordingly, thesecond radiating feed gap 1950 b must propagate one-half the arrivingenergy to deliver one-third of the total energy to tissue. Finally,one-third of the total energy arrives at the third radiating feed gap1950 c, therefore, the third radiating feed gap 1950 c must propagateone-hundred percent of the arriving energy to deliver one-third of thetotal energy to tissue.

In FIG. 19A, the radiating portion 100, with a plurality of radiatingslots 1973 a-1973 c, includes a conductive mesh structure 1972 thatcenters the radiating portion within the conductive mesh structure 1972and includes a plurality of windows 1973 a-1973 d for deliveringdenervation energy to tissue through the windows 1973 a-1973 d. In someembodiment, each window 1973 a-1973 d is configured to deliverdenervation energy to 90 degrees of the circumference of the conductivemesh structure 1972. In some embodiments, the radial section of eachwindow is related to the total number of windows.

In some embodiments, the dielectric constant of the coaxial insulationD0-D7 is selected to match a particular structure of the radiatingportion 100. For example, the dielectric constant of the proximalcoaxial insulation D0 may be related to the dielectric constant of theflexible coaxial cable 1832, and the dielectric constant of theremaining coaxial insulation D0-D7 is related to the specific section ofthe radiating portion 100.

In some embodiments, the width of each feed gap 1950 a-1950 c varies topromote even energy delivery to each slot, as discussed in detailhereinbelow (see FIGS. 51 and 53).

In some embodiments, the proximal mesh structure 1972 a and the distalmesh structure 1972 b are configured to provide minimal restriction offluid flow therethrough. A sufficient flow of fluid through the proximalmesh structure 1972 a and the distal mesh structure 1972 b provides acooling effect and may prevent clotting. In some embodiments, themicrowave energy delivery system halts the delivery of the microwaveenergy power signal if the blood temp approaches and/or rises aboveclotting levels.

As illustrated in FIG. 19B, each window 1973 a-1973 d deliversdenervation energy to a corresponding target tissue 1974 a-1974 d on therenal artery RA wherein at least a portion of tissue along the entirecircumference of the renal artery RA is targeted along the longitudinallength thereof.

In some embodiments having a plurality of feed gaps, a plurality ofcorresponding conductive mesh structures 2072 a-2072 c is provided, asillustrated in FIG. 20. Each feed gap 2050 a-2050 c is operativelyassociated with an individual conductive mesh structure 2072 a-2072 c.Each individual conductive mesh structure 2072 a-2072 c may include avariable mesh density construction and/or one or more windows 2073a-2073 c, as described herein. As illustrated in FIG. 20, theorientation of the windows 2073 a-2073 c may be arranged to radiate indiffering directions (e.g. distributed radially). In some embodiments,the windows 2073 a-2073 c may be arranged to radiate in a similardirection (e.g., indexed radially).

One or more of the conductive mesh structures 2072 a-2072 c may beindependently rotatable around a longitudinal axis of the flexiblemicrowave catheter 2030, either individually or in tandem. One or morecorresponding actuators 15 g (see FIG. 7) may be provided, e.g., on thecatheter hub 18 (see FIG. 7), and may enable remote positioning and/ormonitoring of the conductive mesh structures 2072 a-2072 c.

An individual actuator may be selectively associated to one or moreconductive mesh structures 2073 a-2073 c, thereby enabling the surgeonto manipulate/rotate arbitrary combinations of the conductive meshstructures 2072 a-2072 c as desired. For example, and withoutlimitation, each conductive mesh structure 2072 a-2072 c may beassociated with a switch that, when thrown, operatively couples therespective mesh structure to a dial actuator. One or more conductivemesh structures 2072 a-2072 c may be selected in this manner such that,as the dial actuator is turned, the chosen conductive mesh structures2072 a-2072 c rotate accordingly. Other actuator control schemes andcoupling arrangements may additionally or alternatively be included in acatheter or system in accordance with the present disclosure, includingelectromechanical or mechanical, utilizing, without limitation, aclutch, a pawl, a hydraulic coupling, a magnetorheological coupling, amotor, a stepper, one or more gears, one or more rollers, one or morepulleys, and so forth.

As illustrated in FIG. 21, a flexible microwave catheter 2130 inaccordance with the present disclosure may include one or more meshstructures 2172 a-2172 d arranged between, or adjacent to, one or morefeed gaps 2150 a-2150 c. The mesh structures 2172 a-2172 d may beindividually or collectively expandable and/or collapsible. The flexiblemicrowave catheter may include an outer sheath 2135 that may be drawndistally to selectively deploy one or more of the mesh structures 2172a-2172 d to vary the region of energy delivery. The dimensions of thefeed gaps 2150 a-2150 c e.g., the length L1-L3 of each feed gap 2150a-2150 c, may be tailored to distribute the denervation energy (e.g.,the microwave energy) around the feed gaps 2150 a-2150 c as describedherein. A length of transitional dielectric 2126 a-2126 c having agenerally tubular shape may be coaxially disposed about the exposedinner conductor 2120 in one or more of the feed gaps 2150 a-2150 c,which may load each section, improve impedance matching, reducereflections and/or standing waves, improve efficiently, and reduce therisk of embolism (e.g., clotting).

The mesh structures 2172 a-2172 d are configured to center the radiatingportion 100 within the tubular body structure or body portion (e.g.,renal artery RA). In some embodiments, the tubular body structure maynot be uniformly shaped and the diameter of each of the mesh structuresmay vary to accommodate the non-uniform shape of the tubular bodystructure thereby centering the radiating portion 100 within the tubularbody structure or body portion. Each of the mesh structures 2172 a-2172d may be formed from different materials. In some embodiments, one ormore of the mesh structures 2172 a-2172 d may be configured to functionas a choke or balun thereby preventing at least a portion of themicrowave energy signal from propagating longitudinally beyond the meshstructure 2172 a-2172 d. For example, in one embodiment the proximalmesh structure 2172 a and distal mesh structure 2172 d include aconductive material and configured to function as a choke or balunthereby preventing at least a portion of the microwave energy signalfrom propagating proximally from the proximal mesh structure 2172 a anddistally from the distal mesh structure 2172 d (e.g., reducespropagation of microwave energy from the radiating portion in an axialdirection).

In some embodiments, the proximal mesh structure 2172 a and/or thedistal mesh structure 2172 d have a higher density to act as aneffective electrical wall at the operational frequency of the radiatingportion 100

In some embodiments, each of the mesh structures 2172 a-2172 d form achoke or balun thereby limiting the propagation of energy generated byeach of the feed gaps 2150 a. As illustrated in FIG. 21A, the distalportion of the flexible microwave catheter 2150 may be defined by zonesD0-D7. Energy radiated in zone D0 is limited by the proximal meshstructure 2172 a. Each mesh structure 2172 a-2172 d limits microwaveenergy in zones D1, D3, D5 and D7, respectively. The energy in zone 2 islimited to the energy radiated by first feed gap 2150 a, the energy inzone 4 is limited to energy radiated by second feed gap 2150 b, and theenergy in zone 6 is limited to energy radiated by third feed gap 2150 c.

In some embodiments, the proximal and/or distal surfaces may beselectively coated on a proximal and/or a distal surface with aconductive film, foil, and/or ink to enhance energy directionality.

As illustrated in FIGS. 22A-23B, a flexible microwave catheter 2230 inaccordance with the present disclosure includes a distal mesh basketstructure 2278 a, 2278 b having a basket-like and/or an umbrella-likeshape. Distal mesh basket structure includes a distal apex and aproximal open (expandable) end. The apex of the distal mesh basketstructure is anchored to, or adjacent to, a distal cap 2233 of theflexible microwave catheter 2230. By this arrangement, the distal meshbasket structure may capture any embolic material that may form duringuse, e.g., to prevent clots and other biomaterials from entering thebloodstream.

In FIG. 22A, the distal mesh basket structure 2278 a and the meshstructure 2272 a are configured to center the feed gap 2250 of theradiating portion 100 in the tubular body structure (e.g., renal arteryRA) and/or improve the delivery of denervation energy by preventing orreducing the distal propagation of energy, as described herein.

In FIG. 22B, radiating portion 100 includes distal and proximal meshstructures for centering the feed gap 2250 of the radiating portion 100in the natural body lumen (e.g., renal artery RA). The distal meshbasket structure 2278 b is connected to the cap 2233 via a tether 2278c. Tether 2278 c may be released by the rotating actuator 15 g in thecatheter hub 18 (see FIG. 7) or tether 2278 c may be incorporated into aguide wire system.

As illustrated in FIG. 23, a stepped flexible microwave catheter 2330 inaccordance with the present disclosure includes a stepped configurationwherein a proximal portion 2330 a has a first, larger diameter and adistal portion 2330 b has a second, smaller diameter. Generally, theamount of power deliverable by a system is determined, at least in part,by the size of the conductors therein. Larger proximal portion 2330 acan accommodate a larger diameter flexible coaxial cable 2332 a withconductors can handle more power than smaller conductors. Largerconductors tend to be less flexible than thinner conductors.Advantageously, the thinner, more flexible distal flexible coaxial cable2332 c of the disclosed stepped flexible microwave catheter 2330 enablesfacile feeding of the distal portion 2330 b of the stepped flexiblemicrowave catheter 2330 within the circuitous confines of a tubular bodystructure (e.g., the renal artery) or other body portion, while thelarger, proximal portion 2330 a of the stepped flexible microwavecatheter 2330 is well suited for the larger, straighter tubular bodystructure (e.g., the femoral artery). The amount of energy deliverableto the targeted site may be increased, since the losses are reduced inthe proximal portion 2330 a of the stepped flexible microwave catheter2330.

The flexible coaxial cable 2332 a, 2332 b in the respective proximal anddistal portions 2330 a, 2330 b of the stepped flexible microwavecatheter 2330 are coupled by a tapered matching network 2332 c. Thetapered matching network 2332 c may include a linear tapered portionand/or an exponential tapered portion. Additionally or alternatively,different dielectric layers may be utilized within the flexible coaxialcable 2332 in the proximal section 2330 a, the tapered section 2332 c,and/or the distal section 2332 c to improve matching, reducereflections/standing waves (VSWR), and reduce losses.

As illustrated in FIG. 24, in some embodiments in accordance with thepresent disclosure, the radiating portion of a flexible microwavecatheter 2430 for natural lumens includes an inflatable balloon 2479formed from biocompatible elastomeric material. The inflatable balloon2479 may be inflated with any suitable media, including withoutlimitation a dielectric fluid (e.g., saline or deionized water) and/or agas (e.g., air, CO₂, etc.) In some embodiments, the feed gap 2450 may beincluded within the inflatable balloon 2479 and the dielectric fluidand/or a portion of the inflatable balloon may form part of ananatomical resonant structure as discussed herein. The inflatableballoon 2479 may include one or more conduits or channels disposed in agenerally longitudinal orientation that are arranged to facilitate theflow of vascular fluid (e.g., bloodflow) past the balloon while in use(see FIGS. 25A-25B and 26A-26C). One or more fluid ports may be providedin a proximal portion of the catheter and/or the tip of the catheterthat are in fluid communication with the one or more balloon conduits toenhance the flow of vascular fluid therethrough. At least a part of theballoon may include a conductive layer disposed thereon (see FIGS.58A-58D). The conductive layer may be disposed on an outer surface, orpreferably, an inner surface of the balloon. The conductive layer may beformed by any suitable manner of coating or deposition, includingwithout limitation, thin film deposition, plating, application ofconductive ink, foil, and the like. In some embodiments, the conductivelayer is formed from conductive silver ink. The conductive layer may beformed in a pattern, e.g., a spiral pattern, a lattice pattern, ahalftone pattern, a gradient pattern, or any pattern that facilitatesthe elastic inflation and deflation of the balloon while maintainingconductivity among and between the elements of the conductive layerpattern. In some embodiment, spiral regions of transparent (e.g., no inkcoverage) may have a width of about 3-5 mils (0.003″-0.005″). By thisarrangement, a Faraday cage may be formed by the conductive layer, whichmay improve the radiation pattern and hence delivery of denervationenergy. For example, and without limitation, a balloon in accordancewith this disclosure may include a spiral conductive pattern disposed atthe proximal and distal ends thereof, while having little, or no,conductive material along the middle portion. In embodiments, theballoon structure may include conductive patterns arranged in accordancewith the heretofore described configuration(s) of a mesh structure,e.g., a windowed balloon (having conductive coating on all but awindowed portion of the balloon), multiple balloons, a single balloonwith multiple windows, rotatable balloon(s), and so forth.

FIG. 25A illustrates a microwave energy delivery system 2512 accordingto some embodiments of the present disclosure that includes a catheterhub 2518 connected to a flexible microwave catheter 2530 with a distalradiating portion within an inflatable balloon 2579 on the distal endthereof. System 2512 only illustrates aspects related to the inflatableballoon 2579 although it is understood that any aspect or embodimentdescribed herein may be incorporated into the system 2512.

Balloon catheter hub 2518 includes a balloon fluid coupler 2545 forinflating and/or deflating the inflatable balloon 2579. Balloon catheterhub 2518 may also include any other aspects of the catheter hubs 18 andcoupler 45 or adjustable fluid coupler 845 described herein (see FIGS.7-9C). Balloon fluid coupler 2545 forms inflow and outflow ports 2542 a,2543 a that are in fluid communication with inflow and outflow plenums2542 b, 2543 b, respectively. Inflow and outflow plenums 2542 b, 2543 bare in fluid communication with respective inflow and outflow fluidpassageways 2544 a, 2544 b formed between a fluid flow lumen, theflexible coaxial cable 2532 and the outer sheath 2535.

As illustrated in FIGS. 25A-25B, inflatable balloon 2579 includes aninflatable material 2579 a that forms the outer surface of a ballooncavity 2579 b. Balloon cavity 2579 b may include one or more chambersformed by each balloon lobe 2579 b-2579 d. In some embodiments,inflatable balloon 2579 includes three lobes 2579 b-2579 d wherein thecavities formed by each balloon lobe 2579 b-2579 c are inflated by fluidprovided from the inflow fluid passageway 2544 a.

Balloon lobes 2579 b-2579 d are configured to center the radiatingportion 100 in a body lumen or body portion. Balloon lobes 2579 b-2579 dprovide a passageway for fluid to pass between each balloon lobe 2579b-2579 d and the body lumen wherein fluid flow provides cooling to theballoon lobes 2579 b-2579 d and the body lumen.

Maintaining sufficient blood flow past the radiating portion is criticalin cases, such as balloon centering devices, where the device wouldotherwise block critical blood flow to distal tissues. As such, any ofthe inflatable balloons 2579 described herein, in addition to any of theother centering devices and flexible microwave catheters 30, may be madeto have multiple invaginations (e.g., pleats, channels or interfoldingparts), about its circumference such that fluid (blood) may continue topass over the structure while it is placed.

Fluid from the inflow fluid passageway 2544 a is delivered to thedistal-most portion of the balloon cavity 2579 b, adjacent the cap 2533.Fluid exits the balloon cavity 2579 b through the outflow fluidpassageway 2544 b connected to the proximal-most portion of the ballooncavity 2579 b. As such, fluid travels proximally through the ballooncavity 2579 b thereby proving an additional cooling source to theradiating portion 100. In some embodiments, fluid flow is needed todissipate heat generated by the radiating portion 100 and to maintain adielectric buffer.

Inflatable balloon 2579 may be pre-formed to include the balloon lobes2579 b-2579. In some embodiments, the inflatable material 2579 a isjoined to the radiating portion 100 between each lobe 2579 b-2579 d.

System 2512 may include pressure regulation to maintain pressure in theinflatable balloon 2579. Maintaining pressure may be required tomaintain antenna position and to maintain the passageway between theinflatable balloon and the body lumen. Pressure regulation may beaccomplished by regulating the pressure at the outflow port 2542 a usinga pressure sensor as feedback to the pump or mechanical regulator in thefluid cooling system 40 (See FIG. 7). Pressure regulation may beachieved by maintaining a differential pressure between the inflow port2542 and the outflow port 2543 a with a differential pressure regulator2534 d in the balloon fluid coupler 2545.

In some embodiments, fluid in the inflatable balloon is expelled intothe tubular lumen and/or body structure. Inflatable balloon 2579receives fluid from an inflow fluid passageway 2544 a. To maintainpressure in the inflatable balloon 2579 and/or to maintain the shape ofinflatable balloon 2579, fluid in the inflatable balloon 2579 escapesthrough an orifice formed in the inflatable material 2579 a. The amountof fluid expelled into the tubular lumen and/or body structure maydepend on the length of the procedure and the size of the orifice.

The pressure may also be regulated by performing an anatomicalmeasurement. For example, if used in a vascular system, the pressure inthe inflatable balloon 2579 may also be regulated using a pressuresensor 2542 e to detect the systolic blood pressure pulses inside theinflatable balloon 2579. Pressure pulses measured inside of theinflatable balloon 2579 would increase as the vascular structure becamemore occluded by inflation of the inflatable balloon 2579 and decreasingpressure pulses would indicate a less inflated balloon 2579.

FIGS. 26A-26C illustrate another embodiment of an inflatable balloon2679 for centering a radiating portion in a body lumen (e.g., renalartery RA). Inflatable balloon 2679 includes first, second, and thirdlobes 2679 b-2679 d that are joined to an inflatable balloon housing2679 e. Inflatable balloon housing 2679 e forms an internal chamber thathouses cooling fluid. Cooling fluid from the inflatable balloon housing2679 e flows to the first, second, and third lobes 2679 b-2679 d via aplurality of inflow fluid passageways 2644 a.

FIGS. 27A-41B illustrate various centering devices that may be used toposition a radiating portion according to the present disclosure withina body lumen or body structure. One or more centering device may beconnected to any portion of the flexible microwave catheter. In someembodiments the centering devices are connected to a deployable portionwherein in a first undeployed position, the centering device is in aconstrained condition, and in a second deployed position, the centeringdevice is in an unconstrained condition, e.g., expanded and configuredto center the radiating portion in the body lumen.

FIGS. 27A-27D illustrate centering fins 2790 for centering a radiatingportion 100 in a body lumen BL. Centering fins 2790 include first,second, and third fins 2790 a-2790 c that connect to a portion of aflexible microwave catheter 2730. FIG. 27A illustrates the centeringfins 2790 restrained within the outer sheath 2735. Centering fins 2790are illustrated distal to the radiating portion 100 however centeringfins 2790 may be positioned adjacent or proximal the radiating portion100. FIG. 27B is a transverse cross-section of FIG. 27A that illustrateseach of the fins 2790 a-2790 c restrained by the outer sheath 2735 andoffset by about 120 degrees with respect to each other.

In FIGS. 27C-27D the centering fins 2790 and radiating portion 100 aredeployed from the outer sheath 2735. Fins 2790 a-2790 c, when releasedfrom the constraints of the outer sheath 2735, center the radiatingportion 100 about the center of the body lumen BL. After use, thecentering fins 2790 and radiating portion 100 are retracted to aconstrained position (see FIG. 27A) within the outer sheath 2735.

As illustrated in FIG. 27C, centering fins 2790 may center the radiatingportion 100 by contacting with the body lumen BL. In some embodiments,centering fins 2790 self center the radiating portion 100 viafluid/hydrodynamic, and/or mechanical forces within the body lumen BLthereby ensuring even energy delivery.

In some embodiments, cap 2733 extends distally from the flexiblemicrowave catheter 2730 and longitudinally positions the radiatingsection 100 adjacent a targeted tissue in a body lumen. For example, cap2733 may be dimensioned to enter, and/or become lodged in, a branch ofthe renal artery at the hilum of the kidneys. The distance between thecap 2733 and the radiating portion 100 is dimensioned such that theradiating portion 100 is positioned adjacent a target tissue in therenal artery.

FIG. 28 illustrates a four-prong centering device 2891 that includesfour prongs 2891 a-2891 d that connect to a distal receiver 2891 e andform a proximal receiver 2891 f. Distal receiver 2891 e and proximalreceiver 2891 f are each configured to receive a portion of a flexiblecoaxial cable (not shown) therethrough.

FIGS. 29-32 illustrate a centering basket 2992 for centering a radiatingportion 100 in a body lumen BL. Each centering basket 2992 includefirst, second, third, and fourth bands 2992 a-2992 d that connect toproximal receiver 2992 e and distal receiver 2992 f. In someembodiments, at least one of the proximal receiver 2992 e and the distalreceiver 2992 f is fastened to a portion of the flexible microwavecatheter while the other slides freely of the flexible microwavecatheter. As such, in a deployed condition the centering basket 2992 isexpanded, as illustrated in FIG. 29. In an undeployed condition (e.g.,constrained with an outer sheath or similar device) the bands 2992a-29992 d are compressed thereby elongating the centering basket 2992.

In FIG. 29, the proximal receiver 2992 e is distal to the radiatingportion 100 and connected to the elongated cap 2933. Distal receiver2992 f is unrestrained and extends distally from the elongated cap 2933.In some embodiments, distal end of elongated cap 2933 includes a roundedsurface to facilitate insertion and/or navigation of the flexiblemicrowave catheter 2930 to a targeted tissue.

In FIG. 30, the centering basket 3092 is positioned proximal theradiating portion 100. The distal receiver 3092 e is fastened to theflexible microwave catheter 3030. Proximal receiver 3092 f slides freelyover the flexible microwave catheter 3030 thereby allowing the centeringbasket 3092 to be compressed and elongated when constrained within anouter sheath or similar device (not explicitly shown).

In FIG. 31, the centering basket 3192 is centered about the radiatingportion 100 wherein the distal receiver 3192 e is fastened to theflexible microwave catheter 3130 between the radiating portion 100 andthe cap 3122. The proximal receiver 3192 f slides freely over theflexible microwave catheter 3030 proximal the radiating portion 100,thereby allowing the centering basket 3192 to be compressed andelongated when constrained within an outer sheath or similar device.

In FIGS. 32A and 32B, a proximal centering basket 3292 a and a distalcentering basket 3292 b are connected to the flexible microwave catheter3230. The proximal centering basket 3292 a and the distal centeringbasket 3292 b are configured to center the radiating portion 100 thatincludes a proximal feed gap 3250 a and a distal feed gap 3250 b in FIG.32A and a proximal feed gap 3250 a in FIG. 32B. The proximal centeringbasket 3292 a is positioned proximal to the proximal feed gap 3250 a andthe distal receiver 3292 ae is fastened to the flexible microwavecatheter 3230. Proximal receiver 3292 af of the proximal centeringbasket 3292 a slides freely over the flexible microwave catheter 3230,thereby allowing the proximal centering basket 3292 a to be compressedand elongated when constrained within an outer sheath or similar device(not explicitly shown).

In FIG. 32B, the distal centering basket 3292 b is centered on thedistal feed gap 3250 b wherein the distal receiver 3292 be is fastenedto the flexible microwave catheter 3230 between the distal feed gap 3250and the cap 3233. The proximal receiver 3292 bf of the distal centeringbasket 3292 b slides freely over the flexible microwave catheter 3230proximal the distal feed gap 3250 b, thereby allowing the distalcentering basket 3292 b to be compressed and elongated when constrainedwith an outer sheath or similar device.

In FIG. 32B, the proximal feed gap 3250 a is centered between theproximal centering basket 3292 a and the distal centering basket 3292 b.In some embodiments, the proximal centering basket 3292 a is positionedproximal to the proximal feed gap 3250 a and the distal receiver 3292 aeis fastened to the flexible microwave catheter 3230 such that theproximal receiver 3292 af of the proximal centering basket 3292 a slidesfreely over the flexible microwave catheter 3230. The distal centeringbasket 3292 b is positioned distal to the proximal feed gap 3250 a andthe distal receiver 3292 be is fastened to the flexible microwavecatheter 3130 proximal the cap 3233 such that the proximal receiver 3292bf slides freely over the flexible microwave catheter 3230. As such, theproximal and distal centering baskets 3292 a, 3292 b may be compressedand elongated when constrained with an outer sheath or similar device.

In FIG. 33, a dual-band centering device 3393 is centered about the feedgap 3250 of the radiating portion 100. Dual-band centering device 3393includes a proximal receiver 3393 f that is fastened to the flexiblemicrowave catheter 3333, and a distal receiver 3393 b that slides freelyover the cap 3333 of the flexible microwave catheter 3330.

Dual-band centering device 3393 includes a first and second bands 3393a, 3393 b, respectively, that are offset 180 degrees from each other. Assuch, the dual-band centering device 3393, when expanded in a body lumenBL, elongates the body lumen BL with respect to the first and secondbands 3393 a, 3393 b while drawing the body lumen BL toward the feed gap3350 of the radiating portion 100 (e.g., along each of the side of thedual-band centering device 3393). In this manner, the dual-bandcentering device 3393 shapes the body lumen into an oblong shape whereinthe portion drawn toward the feed gap 3350 will generate hot spots dueto the oblong coaxial arrangement.

In FIG. 34, a clover-leaf centering device 3494 is connected to the cap3433 distal to the feed gap 3450 of the radiating portion 100.Clover-leaf centering device 3494 includes a plurality of petals 3494a-3494 d equally spaced about the circumference of the flexiblemicrowave catheter 3430. Petals 3494 a-3494 d may be formed from ashape-memory material, such as nitonal, such that the petals 3494 a-3493d expand outward to form the clover-leaf shape after being deployed fromthe outer sheath 3435.

In some embodiments, a clover-leaf centering device 3494 is electricallyisolated from the radiating portion 100. Clover-leaf centering device3494 may be joined by a dielectric having adhesive properties (e.g.,dielectric glue) thereby preventing metal-to-metal contact between thepetals 3494 a-3494 d of the clover-leaf centering device 3494 and/or anymetallic portion of the in the radiating portion 100.

In FIG. 35, a flexible microwave catheter 3530 includes a clover-leafcentering device 3594 and a centering basket 3592. Clover-leaf centeringdevice 3594 is joined to the distal cap 3533 and positioned distal thefeed gap 3550 of the radiating portion 100. Centering basket 3592 ispositioned on a portion of the flexible microwave catheter 3530 proximalto the feed gap 3550.

FIGS. 36A and 36B illustrate a paddle centering device 3695 according tosome embodiments of the present disclosure. Paddle centering device 3695includes first, second, and third paddles 3695 a-3695 c fixed to aportion of the flexible microwave catheter 3650. Paddles 3695 a-3695 cmay be fixed by a hinge-like attachment 3695 d that pivotally attachesand/or hingedly attachments each paddle 3695 a-3695 c to the flexiblecoaxial cable 3632.

In FIG. 36A, the paddles 3695 a-3695 c of the paddle centering device3695 are constrained within the outer sheath 3635 of the flexiblemicrowave catheter 3630. In the constrained condition, the paddles 3695a-3695 c are folded inward and positioned adjacent the flexible coaxialcable 3632.

In FIG. 36B, the flexible coaxial cable 3632 and paddles 3695 a-3695 care shown deployed from the outer sheath 3635 of the flexible microwavecatheter 3630. Paddles 3695 a-3695 c are opened by moving each paddleabout the hinge-like attachment. In the open position, paddles 3695a-3695 c are prevented from over-extending by a paddle stop 3695 e,and/or motion is limited by the hinge-like connection 3695 d. In someembodiments, the paddle stop 3695 e is a choke or balun formed on theflexible coaxial cable 3532.

Paddles 3695 a-3695 c may articulate between a closed condition, asillustrated in FIG. 36A, and an open condition, as illustrated in FIG.36B. In some embodiments, articulation may be affected by an actuator onthe catheter hub 18 (see FIG. 7). In some embodiments, articulation maybe affected by the deployment of the flexible coaxial cable 3632 fromthe outer sheath 3635.

Paddle centering device 3695 may include any number of paddles 3695a-3695 c symmetrically positioned (e.g., regularly distributed) aboutthe flexible microwave catheter 3730. In some embodiments, the paddles3695 a-3695 c are substantially identical in length and width, althoughin some embodiments, paddles 3695 a-3695 c may vary in length and/orwidth thereof.

FIGS. 37A and 37B illustrate a dual paddle centering device 3795according to some embodiments of the present disclosure. Dual paddlecentering device 3795 includes a proximal paddle centering device 3795 aand a distal paddle centering device 3795 b. Proximal paddle centeringdevice 3795 a is positioned on the flexible microwave catheter 3730between the first feed gap 3750 a and the second feed gap 3750 b. Distalpaddle centering device 3795 b is positioned on the flexible microwavecatheter 3730 between the second feed gap 3750 b and the third feed gap3750 c. Proximal paddle centering device 3795 a and a distal paddlecentering device 3795 b center the first feed gap 3750 a, second feedgap 3750 b, and third feed gap 3750 c in the body lumen BL.

FIGS. 38A and 38B illustrate a paddle centering device 3896 according tosome embodiments of the present disclosure. Paddle centering device 3896includes first, second, and third paddles 3896 a-3896 c fixed to aportion of the flexible microwave catheter 3830. Paddles 3896 a-3896 cmay be fixed by a hinge-like attachment 3996 d that pivotally attachesand/or hingedly attaches each paddle 3896 a-3896 c to the flexiblemicrowave catheter 3850.

In FIG. 38A, the paddles 3896 a-3696 c of the paddle centering device3896 are constrained within the outer sheath 3835 of the flexiblemicrowave catheter 3830. In the constrained condition, the paddles 3896a-3896 c are folded inward and positioned adjacent the flexible coaxialcable 3832.

In FIG. 38B, the flexible coaxial cable 3832 and paddles 3896 a-3896 care shown deployed from the outer sheath 3835 of the flexible microwavecatheter 3830. Paddles 3896 a-3896 c are opened by moving each paddleabout the hinge-like attachment. In the open position paddles 3896a-3896 c are prevented from over-extending by a paddle stop (e.g., outersheath 3835) and/or motion is limited by the hinge-like connection 3896d.

Paddles 3896 a-3896 c may articulate between a closed condition, asillustrated in FIG. 38A, and an open condition, as illustrated in FIG.38B. In some embodiments, articulation may be affected by an actuator onthe catheter hub 18 (see FIG. 7). In some embodiments, articulation maybe affected by the deployment of the flexible coaxial cable 3832 fromthe outer sheath 3835.

Paddles 3896 a-3696 c may open in a direction opposite the fluid flowFF, as illustrated in FIG. 38B or paddles 3695 a-3695 c (see FIGS.36A-36B) may open in the same direction as the fluid flow FF.

FIGS. 39A and 39B illustrate a dual paddle centering device 3996according to some embodiments of the present disclosure. Dual paddlecentering device 3996 includes a proximal paddle centering device 3996 aand a distal paddle centering device 3996 b. Proximal paddle centeringdevice 3996 a is positioned on the flexible microwave catheter 3930proximal the first feed gap 3950 a. Distal paddle centering device 3996b is positioned on the flexible microwave catheter 3930 between thefirst feed gap 3950 a and the second feed gap 3950 b. Proximal paddlecentering device 3996 a and a distal paddle centering device 3996 bcenter the first feed gap 3950 a and second feed gap 3950 b in the bodylumen BL.

FIGS. 40A and 40B illustrate a deployable centering device that centersthe distal radiating portion 100 of a flexible microwave catheter 4030with a plurality of tines 4097. In an undeployed condition, asillustrated in FIG. 40A, the tines are restrained within the outersheath 4035 of the flexible microwave catheter 4030. Outer sheath 4035may retract proximally thereby deploying the radiating portion 100 andtines 4097 from the outer sheath 4035. Alternatively, radiating portion100 and tines 4097 may deploy distally from the outer sheath 4035. In adeployed condition, as illustrated in FIG. 40B, the tines are attachedto, and extend radially outward from, the flexible microwave catheterthereby centering the radiating portion in the renal artery RA.

FIG. 41A illustrates a helical centering device 4198 that may be used tocenter the distal radiating portion 100 of a flexible microwave catheter4030. Helical centering device 4198 includes a plurality of helical ribs4198 a-4198 c that each connect to the outer surface of a distal end ofthe flexible microwave catheter 4130 a. In some embodiments, the helicalribs 4198 a-4198 c are attached to the outer surface of the flexiblecoaxial cable 4032 a. In an undeployed condition, the helical ribs 4198a-4198 c are compressed between the flexible coaxial cable 4032 a andthe inner surface of the outer sheath 4035. As the helical centeringdevices are deployed from the outer sheath 4025, each of the helicalribs 4198 a-4198 c extends radially from the flexible coaxial cable 4032a thereby centering the radiating portion 100 within a body lumen.

FIG. 41B illustrates a helical centering device 4199 configured toinsert over the distal portion of a flexible microwave catheteraccording to embodiments of the present disclosure. Helical ribs 4199a-4199 c attach to the outer surface of a helical sleeve 4199 d and thehelical sleeve is configured to slidably engage the distal portion of aflexible microwave catheter.

FIGS. 42-44 illustrate a flexible microwave catheter 30 including anouter sheath 135 that forms the outer layer of the flexible microwavecatheter 30 and a flexible coaxial cable 32 that slidably engages theinner surface of the outer sheath 135. The proximal portion of the outersheath 135 includes a first inner diameter D1 that accommodates theouter diameter of the outer conductor 124. A distal-most portion of theouter sheath 135 forms a sliding hub 135 a that accommodates theradiating portion 100 of the flexible coaxial cable 32. Sliding hub 135a includes a second inner diameter D2 that accommodates the outerdiameter of the outer dielectric insulating layer 128, wherein the firstinner diameter D1 of the outer sheath 135 is less than the second innerdiameter D2 of the sliding hub 135 a. As such, a mechanical stop 129 isformed by the transition of the outer sheath 135 between the first innerdiameter D1 and the second inner diameter D2.

In some embodiments, sliding hub 135 a is less flexible than theproximal portion of the flexible microwave catheter 30. In someembodiments, sliding hub 135 a is rigid. Flexible microwave catheter 30may also include a guidance system (not explicitly shown) formanipulating the angle between a proximal, more flexible portion of theflexible microwave catheter 30 and a distal, less-flexible and/or rigid,portion of the flexible microwave catheter (e.g., sliding hub 135 a).

An outer surface of the outer sheath 135 may include a dielectriccoating. In one embodiment, the dielectric coating is a chemically vapordeposited polymer such as the coating sold and manufactured by ParyleneCoating Services of Katy, Tex., under the tradename Parylene™. Inanother embodiment, the dielectric coating includes one or more bloodclot reducing properties or components.

FIGS. 42, 43 and 44 illustrate the flexible coaxial cable 32 and theradiating portion 100 on the distal end thereof positioned in variouspositions, e.g., positioned in a fully retracted position (see FIG. 42),in a partially deployed position (see FIG. 43), and in a fully deployedposition (see FIG. 44).

Turning now to FIG. 42, the radiating portion 100 is fully retractedwithin the sliding hub 135 a of the outer sheath 135. In a fullyretracted condition the proximal end of the outer dielectric insulatinglayer 128 abuts the mechanical stop 129 of the outer sheath 135 therebypreventing further retraction of the flexible coaxial cable 32 withinthe outer sheath 135. The proximal end of outer dielectric insulatinglayer 128 may engage the mechanical stop 129 wherein the engagingsurface further prevents retraction of the flexible coaxial cable 32within the outer sheath 135.

Cap 133 abuts the distal end of the outer sheath 135 and forms a smoothtransition between the outer surface of the outer sheath 135 and theouter surface of the cap 133. Cap 133 and outer sheath 135 may be joinedtogether by mechanical engagement, an interference fit, or by soldering,brazing, adhesive and/or laser welding, thereby preventing unintendedseparation (e.g. deployment) between the cap 133 and outer sheath 135.Cap 133 may prevent further retraction of the flexible coaxial cable 32within the outer sheath 135. While the embodiments illustrated hereinillustrate a blunt distal end that enables the flexible microwavecatheter 30 to benignly follow a guiding lumen, in other embodiments,the cap may include a sharpened tip configured for percutaneousinsertion into tissue.

In use, a clinician inserts the flexible microwave catheter 30 (e.g.,radiating portion 100) into a patient through a channel and maneuversthe flexible microwave catheter 30 to a desired position with thepatient. The channel may be a naturally formed body channel and/or lumen(e.g. artery vein, esophagus, bronchial, anus, vagina, urethra, and soforth), a lumen inserted in a naturally formed body channel, a cannula,a shaft or any other suitable insertion needle, device, guide, orsystem.

During an insertion step, the radiating portion 100 is housed in thesliding hub 135 a of the outer sheath 135. Sliding hub 135 a engagesouter conductor 124 and prevents any unintended release of energy topatient tissue.

Cap 133 may electrically engage outer sheath 135 thereby forming anelectrical pathway (e.g., electrical short) between the inner conductor120 and the outer conductor 124 via a portion of the outer sheath 135.In a fully retracted position, as illustrated in FIG. 42, the entireradiating portion 100 is contained within the outer sheath and cap 133thereby minimizing or eliminating, discharge of electrosurgical energytherefrom.

Turning now to FIG. 43, distally advancing the flexible coaxial cable 32within the outer sheath 135 of the flexible microwave catheter 30deploys the radiating portion 100 from the sliding hub 135 a. The lengthof the radiating portion 100 deployed from the sliding hub 135 a isselectable by the clinician.

With reference to FIGS. 7, 8C and 42-44, at least a portion of theflexible coaxial cable 32 connects to the actuator 15, 815 in thecatheter hub 18. Actuation of the actuator 15, 815 moves the flexiblecoaxial cable 32 and advances and retracts the flexible coaxial cable 32within the outer sheath 35. Actuator 15, 815 may be actuated to anydesirable position along the actuator slot 15 a. The position of theactuator 15, 815 in the actuator slot 15 a is related to the position ofthe radiating portion 100 in the sliding hub 135 a and related to thesection of the radiating portion 100 that deploys from the sliding hub135 a.

Lock mechanism 817 may be integrated into the body 845 a, 854 b of theadjustable fluid coupler 845. In some embodiments, the most-proximalposition of the lock mechanism 817 includes a lock position that locksthe actuator 15, 815 in position to prevent accidental deployment of theradiating portion 100 while positioning the flexible microwave catheter30 in a guiding lumen. In some embodiments, the lock mechanism 817and/or the actuator 15, 815 includes a tensioning mechanism, such as aspring (not explicitly shown) that provides a proximal bias on theflexible coaxial cable 32 when the actuator 15, 815 is in the lockposition. In some embodiments, the lock position of the actuator 15, 815includes a take-up mechanism that compensates for any length changesbetween the flexible coaxial cable 32 and the outer sheath due 35 tobending and/or turning of the outer sheath 35 and flexible coaxial cable32 while positioning the flexible microwave catheter 30 in a guidinglumen. In some embodiments, actuator 15, 815 includes a lock mechanism817, a tensioning mechanism, a take-up mechanism or any combinationthereof. For example, actuator 15, 815 may include a raised portion 817a that mates with a receiver portion 817 b formed on the fluid couplerbody 845 a and the receiver portion 817 b provides a plurality oflongitudinal positions to receive the raised portion 817 a along itslength. Actuator 15, 815 may further include a biasing mechanism, suchas a spring or elastic member, or any other suitable tensioningmechanism and/or take-up mechanism.

FIG. 44 illustrates a cross-sectional view of the distal portion of theflexible microwave catheter 30 with the radiating portion fully deployedfrom the sliding hub 135 a. Proximal portion 128 a of the outerdielectric insulating layer 128 remains housed within the sliding hub135 a in the fully deployed position. Proximal portion 128 a of theouter dielectric insulation layer 128 maintains engagement with thesliding hub 135 a thereby facilitating the subsequent retraction of theradiating portion 100 within the sliding hub 135 a (see FIGS. 42 and43). Proximal portion 128 a may form a fluid-tight seal 121 a with thesliding hub 135 a. Fluid-tight seal 121 a may prevent body fluid fromentering the sliding hub 135 a and filling the void 135 b within thesliding hub 135 a formed by deploying the radiating portion 100.

The transitional dielectric 126 may have dielectric properties relatedto the dielectric properties of the outer dielectric insulating layer128. In some embodiments, a dielectric gradient is formed between thetransitional dielectric 126, the outer dielectric insulating layer 128and the anatomical structures with which the radiating portion 100 maybe used, e.g., the renal artery or other body lumen/body structure).

The outer surface of the outer dielectric insulating layer 128 and theinner surface of the sliding hub 135 a may include interfacing surfaces117 a, 117 b that provide a mechanical stop thus preventing the proximalportion 128 a of the outer dielectric insulating layer 128 fromadvancing from the sliding hub 135 a. For example, in one embodiment,the inner surface of the sliding hub 135 a includes a radially inwardprotruding tab 117 a. At a fully deployed position the radially inwardprotruding tab 117 a engages a mechanical stop 117 b formed in thedielectric insulating layer 128 thereby preventing further distaldeployment of the radiating portion 100 from sliding hub 135 a.

In some embodiments, a choke or balun short (not explicitly shown) ispositioned longitudinally proximal to the formation of the helical feedgap 50 and may be fixed to the outer conductor 124 and/or the outersheath 135. The balun may be formed from a short conductive (e.g.,metallic) ring having an inner diameter dimensioned to accept the outerconductor 124 (or the outer sheath 135). Alternatively, the balun may beformed on the inner surface of the outer sheath 135. The balun iselectrically bonded (e.g., soldered and/or electrically connected by asuitable conductor) to the outer conductor 124. This balun affects aradiofrequency short which, in turn, may optimize, control, focus,and/or direct the general proximal radiating pattern of the radiatingportion antenna, e.g., reduce the propagation of denervation energybeyond the proximal end of the antenna radiating portion and/or thebalun.

The balun assembly may include a balun dielectric sleeve, which may beformed from extruded polytetrafluoroethylene (PTFE, e.g., Teflon®). Thebalun dielectric may be positioned over the radiating portion 100 of theflexible microwave catheter 30 and mated to the balun ring. A length ofheat shrink tubing (not explicitly shown), having a conductive materialon a surface thereof, preferably an inner surface, may be positionedover the PTFE sleeve to improve the performance of the balun and thus,improve the radiating pattern of denervation energy.

In some embodiments, as discussed in detail hereinbelow and illustratedin FIGS. 42-57, a flexible microwave catheter in accordance with thepresent disclosure includes a radiating portion having a spiralconfiguration, wherein the outer conductor of the radiating portion isexposed in a spiral pattern. The width of the spiral opening mayoptionally be tapered, increasing in width as the spiral winds distallyalong the radiating portion, in order to radiate energy evenly along thelength thereof (see FIGS. 42-49 and 54-57). A spiral sensor lumen orconductor may be interspersed within the spiral feedpoint to operativelycouple a sensor disposed at or near the distal region of the probe to agenerator or other apparatus located proximally of the probe.

Any number of baskets, centering devices or expandable members, asdiscussed hereinabove, may be utilized with this spiral structure toselectively ablate tissue in a radial direction away from thecentralized structure. This would allow for a procedure which normallyrequires multiple placements of an ablation device to be simplified bynecessitating only one placement providing multiple selectively directedradiating elements. The user may choose to deploy any number of thebaskets, centering devices or expandable members, while leaving otherscollapsed and thus deactivated due to the conductive sheath covering thefeed gap.

The deployable structure illustrated in FIGS. 42-44 and describedherein, may also be utilized to deploy any of the structures andradiating portion 100 described herein.

As discussed hereinabove with respect to FIGS. 42-44, the radiatingportion 100 includes a shielding outer conductor 124 a that exposes theinner conductor 120 thereby forming a helical feed gap 50 (e.g., feedpoint). In one embodiment, the shielding outer conductor 124 a is formedby removing a portion of the outer conductor 124 at the helical feed gap50. The shielding outer conductor 124 a that remains on the innerconductor 120 is wrapped helically around the longitudinal axis of theinner conductor 120. A helical and/or spiral feed gap provides uniformdistribution of energy along the axial length of the radiation sectionas well as an ideal impedance match to the coaxial waveguide impedancethereby reducing unwanted heating along the flexible coaxial feedline32.

In some embodiments, prior to use (e.g., during manufacturing) the outerconductor 124 and inner dielectric insulator are removed from the innerconductor 120 in the radiating portion 100 and a shielding outerconductor 124 a and shielding dielectric (not explicitly shown) arepositioned on the exposed inner conductor. The shielding outer conductor124 a is wrapped helically around the longitudinal axis of the innerconductor 120. The proximal portion of the shielding outer conductor 124a is electrically connected to the distal portion of the outer conductor124. The distal portion of the shielding outer conductor 124 a iselectrically connected to the cap 133. The cap shorts the shieldingouter conductor 124 a to the inner conductor 120.

Cooling fluid from the fluid cooling system 40 (see FIG. 7) may flowthrough fluid lumens formed in the shielding outer conductor 124 a andconnected to the inflow fluid passageway 44 a and outflow fluidpassageway 44 b in the flexible microwave catheter 30 thereby provingfluid pathways for cooling fluid to flow to and from the distal end ofthe radiating portion 100.

As discussed hereinabove, a transitional dielectric 126 may be disposedin the helical feed gap 150 and may generally and/or geometricallycorrespond to the dimensions of the helical feed gap 150. Thetransitional dielectric 126 and the shielding dielectric (not explicitlyshown) may be formed from similar materials with similar dielectricproperties. In some embodiments, the transitional dielectric 126 and theshielding dielectric may have different dielectric properties. In someembodiments, a single dielectric layer includes the transitionaldielectric 126 and the shielding dielectric includes a first geometricalportion having dielectric properties corresponding to the transitionaldielectric 126 and a second geometrical portion having dielectricproperties corresponding to the shielding dielectric.

As discussed hereinabove, the feed gap 150 is defined by the void formedfrom the removal of a portion of the outer conductor 124. Similarly, thehelical feed gap 150 is defined by the void formed between adjacentwindings of the helically wrapped shielding outer conductor 124 a (e.g.,helically wrapped about the longitudinal axis of the inner conductor120). The dimensions of the helical feed gap 150 are related toproperties and the position of the shielding outer conductor 124 a. Thehelical feed gap 150 may also be defined by the portion of the innerconductor not helically wrapped by the shielding outer conductor 124 a.As such, defining the dimensional properties and position of theshielding outer conductor 124 c necessarily defines the helical feed gap150 that varies along the longitudinal length of the radiating portion100. In one embodiment, the position of the helical feed gap 150 changescircumferentially along the length thereof. In some embodiments, thepitch of the helix (e.g., the width of one complete helix turn, measuredparallel to the axis of the helix) varies along the longitudinal lengthof the radiating portion 100. In some embodiments, the pitch may varydue to a change in the helix angle (e.g., the angle between any helixand an axial line formed perpendicular to the inner conductor). In someembodiments, the pitch may vary due to a change in the width of thehelical feed gap 150 (e.g., a varying thickness of the helical feed gap150 along the longitudinal length thereof). In some embodiments, thepitch may vary due to a change in the helix angle and a change in thewidth of the helical feed gap 150.

In use, the energy transmitted to tissue by the radiating portion 100 isrelated to the area and position of the helical feed gap 150. Asillustrated in FIGS. 42-44, the area of the helical feed gap 150increases as the helix winds distally, transitioning from a narrowhelical feed gap 150 on the proximal end to a wide helical feed gap 150on the distal end of the radiating portion 100. The change in area(e.g., increase in area as the helix distally winds) translates in a lowcoupling factor on the proximal end and a high coupling factor on thedistal end. On the proximal end of the radiating portion 100 thecoupling factor is 1% and the coupling factor increases in anexponential manner to 100% at the distal end.

FIGS. 45 and 46 illustrate another embodiment of a non-linear wrappattern that forms a radiating portion 200 that may be incorporated intoany flexible microwave catheter 30 according to some embodiments of thepresent disclosure. The area of the helical feed gap 250 increases asthe helix winds distally with the proximal end providing a narrow feedgap 250 and the distal portion being more substantially exposed. Thenon-linear change in the area of the helical feed gap 250 at theproximal end of the radiating portion 200 and the area of the helicalfeed gap 250 at the distal end of the radiating portion 200 is due tothe geometry of the shielding outer conductor 224 a.

As illustrated in FIG. 46, the shielding outer conductor 224 a includesa proximal first non-linear edge 224 b, a second distal non-linear edge224 c wherein the first non-linear edge 224 b and the second non-linearedge 224 c terminate on the distal end 224 d thereby forming asubstantially pointed distal end 224 d.

FIGS. 47 and 48 illustrate yet another embodiment of a non-linear wrappattern that forms a radiating portion 300 that may be incorporated intoany flexible microwave catheter 30 of the present disclosure. The areaof the helical feed gap 350 increases as the helix travels distally withthe proximal end providing a narrow feed gap and the distal portionbeing substantially exposed. The non-linear change in the area of thehelical feed gap 350 at the proximal end of the radiating portion 300and the area of the helical feed gap 350 at the distal end of theradiating portion 300 is due to the geometry of the shielding outerconductor 324 a.

As illustrated in FIG. 48, the shielding outer conductor 324 a includesa proximal first non-linear edge 324 b, and a second distal linear edge324 c that terminates on the distal end thereof. The distal end forms aflat distal edge 324 d configured to align with the distal end of theinner conductor (not explicitly shown).

One measure of the varying helical feed gap 150 is the feed gap ratio,defined herein as the ratio between the cross-sectional circumference ofthe helical feed gap 150 and the cross-sectional circumference of theshielding outer conductor 124 a. FIG. 49 is a graph illustrating thefeed gap ratio along the longitudinal length of the radiation portion1000, 200, 300 of the respective embodiments illustrated in FIGS. 44, 45and 47. The feed gap ratio of radiating portion 1000 in FIG. 44 variesbetween 0% and 50% and varies linearly along the longitudinal lengthbetween the proximal end and the distal end of the radiating portion1000. The feed gap ratio of radiation portion 200 in FIG. 45 variesbetween 0% and 100% and varies non-linearly along the longitudinallength between the proximal end and the distal end of the radiatingportion 300. The feed gap ratio of radiation portion 300 in FIG. 47varies between 0% and 100% and varies non-linearly along thelongitudinal length between the proximal end and the distal end of theradiating portion 300. Other geometries that may be used include anexponential taper, a triangular taper and a Klopfenstein logarithmictaper from a stepped Chebyshev transformer where the sections increaseto infinite (e.g., analogous to a Taylor distribution).

As discussed hereinabove with respect to FIGS. 6A-6B and 8A-8C, theflexible microwave catheter 30 may include a tubular inflow lumen 37positioned coaxially between the inner flexible coaxial cable 32 and theouter sheath 135. A clearance between the outer diameter of the flexiblecoaxial cable 32 and the inner diameter of the inflow lumen 37 definesan inflow fluid passageway 44 a. A clearance between the outer diameterof the inflow lumen 37 and an inner diameter of the outer sheath 135defines an outflow fluid passageway 44 b. During use, a coolant, e.g.,carbon dioxide, air, saline, water, or other coolant media may besupplied to the radiating portion 100 by the inflow fluid passageway 44a and evacuated from the radiating portion 100 by the outflow fluidpassageway 44 b.

In some embodiments, the inflow fluid passageway 44 a that suppliescoolant and is the inner-most fluid conduit and the outflow fluidpassageway 44 b that evacuates coolant is the outer-most fluid conduit.In other embodiments, the direction of fluid flow may be opposite. Oneor more longitudinally-oriented fins or struts (not explicitly shown)may be positioned within the inflow fluid pathway and/or the outflowfluid pathway to support and control the position of the inflow lumenwith respect to the outer sheath 135 and to support and control theposition of the flexible coaxial cable 32 with respect to the inflowlumen 37.

FIG. 50 is an electrical circuit diagram of a leaky waveguide accordingto another embodiment of the present disclosure. The leaky waveguideincludes a network with an impedance of Z_(O) wherein all energy isradiated or dissipated in the leaky waveguide. Each Z_(L) is composed ofa radiation resistance, reactive impedance and loss resistance wherein:

Z _(L) =R _(R) −iR _(i) +R ₁  (1)

Although represented by a lumped element, the Z_(L) components may be adistributed network. As illustrated in FIG. 51, each Z_(L) component mayrepresent one of the five slots S1-S5 in a coaxial cable.

Another waveguide according to the present disclosure may include anynumber of slots. FIG. 52 illustrates an embodiment having a radiatingportion 200 utilizing ten (10) slots. To provide a uniform radiatingpattern along the length of the radiating portion, each of the ten (10)slots must radiate approximately 10% of the total available energyprovided to the waveguide Z_(O). Since each slot radiates a portion ofthe total available energy, the remaining energy available to eachsubsequent slot is less than the energy provided to the previous slot.As such, a uniform radiating pattern requires each distally positionedslot to radiate a higher percentage of the remaining available energythan each proximally positioned (e.g., prior) slot.

In the example embodiment illustrated in FIG. 52, 100 Watts of energy isprovided to the leaky waveguide 200, therefore, slot 1 must transmitabout 10% of the total energy provided thereto (e.g., 10% of 100Watts=10 Watts). Slot 2 is provided with about 90 Watts (100 Watts minusthe 10 Watts transmitted by slot 1), therefore, slot 2 must transmitabout 11% of the total energy provided thereto (e.g., 11% of 90 Watts=10Watts). Slot 3 is provided with about 80 Watts (100 W minus the 20 Wattstransmitted by slots 1-2), therefore, slot 3 must transmit about 12.5%of the total energy provided thereto (e.g., 12.5% of 80 Watts=10 Watts).Slot 4 is provided with about 70 Watts (100 Watts minus 30 Wattstransmitted by slots 1-3), therefore, slot 4 must transmit about 14.3%of the total energy provided thereto (e.g., 14.3% of 70 Watts=10 Watts).Slot 4 is provided with about 70 Watts (100 Watts minus 30 Wattstransmitted by slots 1-3), therefore, slot 4 must transmit about 14.3%of the total energy provided thereto (e.g., 14.3% of 70 Watts=10 Watts).Slot 5 is provided with about 60 Watts (100 Watts minus 40 Wattstransmitted by slots 1-4), therefore, slot 5 must transmit about 16.7%of the total energy provided thereto (e.g., 16.7% of 60 Watts=10 Watts).Slot 6 is provided with about 50 Watts (100 Watts minus 50 Wattstransmitted by slots 1-5), therefore, slot 6 must transmit about 20% ofthe total energy provided thereto (e.g., 20% of 50 Watts=10 Watts). Slot7 is provided with about 40 Watts (100 Watts minus 60 Watts transmittedby slots 1-6), therefore, slot 7 must transmit about 25% of the totalenergy provided thereto (e.g., 25% of 40 Watts=10 Watts). Slot 8 isprovided with about 30 Watts (100 Watts minus 70 Watts transmitted byslots 1-7), therefore, slot 8 must transmit about 33% of the totalenergy provided thereto (e.g., 33% of 30 Watts=10 Watts). Slot 9 isprovided with about 20 Watts (100 Watts minus 80 Watts transmitted byslots 1-8), therefore, slot 9 must transmit about 50% of the totalenergy provided thereto (e.g., 50% of 20 Watts=10 Watts). Slot 10 isprovided with about 10 Watts (100 Watts minus 90 Watts transmitted byslots 1-9), therefore, slot 10 must transmit about 100% of the totalenergy provided thereto (e.g., 100% of 10 Watts=10 Watts).

Moving distally along the waveguide, each slot must progressivelytransmit a higher percentage of energy available to the individual slot.One method of progressively increasing the percentage of energytransmitted from each slot is to vary the width of each slot as thewaveguide progresses distally (increasing the width of each slot movingdistally). FIG. 53 illustrates a waveguide wherein each slotprogressively increases in width. In some embodiments the increase inwidth provides an improvement in efficiency thereby resulting in anincrease in the percentage of energy transmitted therefrom. Thedistal-most slot may be regarded as highly efficient slot capable ofradiating the total remaining power therefrom (e.g., radiating 100% ofthe power provided thereto).

The energy radiated from each of the slots is related to the desiredefficiency of the slot, the width of the slot and/or the wavelength ofthe energy provided to waveguide (e.g., each slot). In some embodiments,the width of each slot is related the desired efficiency of the slot.For example, if the desired efficiency of a slot is 20% of the energyprovided thereto, the width may be calculated by the microwave signalwavelength and desired efficiency.

In another embodiment, the effective length of the distal-most slot isequal to ½ of the wavelength of microwave signal, and the width of theslots proximal the distal-most slot is related to the desired efficiencyof the slots wherein the efficiency of each slot is determined by theenergy provided to each individual slot and the desired power output ofeach slot.

Due to losses in the coaxial waveguide, the amount of energy provided toeach slot is equal to the energy provided to the waveguide minus theamount of energy transmitted by the proximal slots and minus any lossesin the coaxial cable. As such, the percentage for each progressive slotmay be increased and/or the number of slots may be decreased tocompensate for the energy losses in the coaxial waveguide.

Using slot 4 in FIG. 52 as an example, and assuming the losses in slots1-3 to equal 5 Watts, the actual energy provided to slot 4 is 65 Watts(100 Watts minus 30 Watts transmitted by slots 1-3 and less the lossesof 5 Watts). Therefore, slot 4 must transmit about 15.4% of the 65 Wattsprovided to slot 4 (e.g., 15.4% of 65 Watts). As such, losses in theproximal slots may result a reduction in the number of slots in order toprovide an even and equal pattern of energy radiation from each slot.

A more distributed approach, as opposed to the segmented approach ofindividual slots, provides an even and uniform energy distributionpattern. FIG. 54 shows a waveguide wherein the progressively increasingwidth of each slot, as illustrated in the waveguide of FIG. 53, isarranged as a continuous helical slot 450. In one embodiment, thegeometry of the slot (e.g., the helix angle, pitch and slot width) isrelated to the required efficiency of each section of the helix. In someembodiments, the efficiency of each section of the helix is determinedby the energy provided to each section of the helix and the desiredpower output of each section of the helix. Geometric parameters that mayvary include the axial ratio, the number of turns and the width of thefeed gap. The helix, which eliminates the individual slots, may alsoreduce losses generated as a result of having each individual slot.

As the opening widens (e.g., in a proximal to distal direction), due tothe change in pitch and/or the change in the helix angle, the slotprogressively radiates more energy thereby promoting a uniform energypattern and resulting in less return loss.

FIGS. 55 and 56 illustrate flexible microwave catheters 530 and 630 withwaveguides 500 and 600 related to the waveguides of FIGS. 53 and 54,respectively. In FIG. 55, the waveguide 500 includes a plurality ofprogressively spaced slots 550 wherein the width of each distally spacedslot increases to provide the desired power output. In FIG. 56, thewaveguide 600 includes a helical feed slot 650 with a varying pitch,slot width and helix angle wherein the progressively increasing slotwidth, and exposed portion of the radiating inner conductor 520, 620,provides the desired power output along the length of the waveguide 600.The flexible microwave catheters 530 and 630 may include a cooling fluidarrangement as discussed hereinabove.

FIG. 57 illustrates waveguides 700 and 800, wherein slotted waveguide700 includes five (5) slots and helix waveguide 800 includes five turnsof a helix. Waveguides 700 and 800 are arranged to provide acomparison/correlation between the slots S1-S5 of the slotted waveguide700 and the respective helix turns HT1-HT5 of the helix waveguide. Eachhelix turn HT1-HT5 includes a corresponding position on the helixwherein the width of the helix is related to the width of thecorresponding slot S1-S5 and the exposed inner conductor 720. Asdiscussed hereinabove, the shape and position of the helix slot HS isrelated to, and defined by, the void between the individual wraps of theshielding outer conductor 824 a on the inner conductor 820.

As further illustrated in FIG. 57, the slotted waveguide 700 includesfive radiation slots S1-S5 with each slot S1-S5 exposing a portion ofthe inner conductor 720. Slots S1-S5 generate a correspondingelectromagnetic field F1-F5, respectively. The electromagnetic fieldsF1-F5 are distinct and independently generated, although at least aportion of one or more of the electromagnetic fields F1-F5 may overlapand/or combine with an adjacent electromagnetic field F1-F5.

The helix waveguide 800 generates a helical-electromagnetic field HFthat extends along the longitudinal length of the helix waveguide 800.The shape of the helical-electromagnetic field HF is related to theshape of the helix slot HS and related to the varying void formedbetween the individual wraps of the shielding outer conductor.

The shape of the helical-electromagnetic field HF may be represented asa plurality of inter-connected, helically-shaped electromagnetic fieldsHF1-HF5 with each of the inter-connected helically-shapedelectromagnetic field being related to a corresponding slot S1-S5 on theslotted waveguide 700. The helical-electromagnetic field HF may includea plurality of minimum nodes and a plurality of maximum nodes whereinthe magnitude of the helical-electromagnetic field at a minimum node isa relative minimum and the magnitude of the helical-electromagneticfield at a maximum node is a relative maximum. In one embodiment, thenumber of minimum nodes is related to the number of helix turns. Theoverall shape of the helical-electromagnetic field HF may dynamicallychange about the helix. In some embodiments, the number of maximum nodesis related to the number of helix turns.

FIG. 58A is a perspective view of a deflated balloon centering device5872 having a spiral window 5899 formed therein according to someembodiments of the present disclosure. Balloon centering device 5872includes a balloon membrane 5872 a coated with a conductive layer 5872b. As illustrated in the cut-out portion of FIG. 58A, conductive layer5872 b may be formed on the inner surface of balloon membrane 5772 a.Alternatively, in some embodiments, the conductive layer 5872 b isformed on the outer surface of the balloon membrane 5872 a.

The conductive layer 5872 b may be formed by any suitable manner ofcoating or deposition, including without limitation, thin filmdeposition, plating, application of conductive ink, foil, and the like.In some embodiments, the conductive layer 5872 b is formed fromconductive silver ink. The conductive layer 5872 b may be formed in apattern, e.g., a spiral pattern, a lattice pattern, a halftone pattern,a gradient pattern, or any pattern that facilitates the elasticinflation and deflation of the balloon centering device 5872 whilemaintaining conductivity among and between the elements that form thepattern of the conductive layer 5872 b.

Spiral window 5899 includes the balloon membrane 5872 a and does notinclude a conductive layer 5872 b. Balloon membrane 5872 a in the spiralwindow 5899 area is formed of a material that is transparent tomicrowave energy thereby exposing the tissue adjacent the spiral window5899 to an application of denervation energy. The spiral window 5899 mayhave a maximum width of about 3-5 mils (0.003″-0.005″). By thisarrangement, the conductive layer 5872 b forms a Faraday cage structurethat improves the radiation pattern and facilitates the delivery ofdenervation energy to the tissue adjacent the spiral window 5899. Insome embodiments, the balloon membrane 5872 may be formed from anon-compliant material to ensure the correct geometer is achieved.

In some embodiments, a balloon centering device 5872 in accordance withthe present disclosure may include a conductive layer 5872 b disposed atthe proximal and distal ends thereof, while having little, or no,conductive material in a conductive layer 5872 b along the middleportion, thereby forming a conductive gradient between the proximal endand distal ends, and the middle portion. The balloon centering device5872 may include conductive patterns arranged in accordance with theheretofore described configuration(s) of mesh structures, wherein theconductive layer 5872 is coated on all but a windowed portion 5899 ofthe balloon centering device 5872. Some embodiments may include multipleballoon centering devices, a single balloon centering device withmultiple windows, a rotatable balloon(s) centering device, and so forth.

Fluid ports 5872 c form a plurality of lumens through the ballooncentering device 5872. The radial position of the fluid ports 5872 c maybe positioned radially outward to provide cooling for the anatomicalstructure. In embodiments, fluid ports 5872 c may be positioned radiallyinward to provide cooling to the radiating portion of the flexiblemicrowave catheter 5830.

FIG. 58B is a perspective view of the balloon centering device of FIG.58A shown fully inflated and positioned within a renal artery RA. Thewindow 5899 extends around about the entire circumference along thelongitudinal length of the balloon centering device 5872. When placed ina body lumen, such as the renal artery RA, the energy applied throughthe window 5899 results in a heating pattern consistent with the shapeof the window 5899.

Fully inflated, the spiral window 5899 may radiate energy over 360degrees along a longitudinal span of about 2 to 3 cm. In other bodylumens, the spiral window 5899 may radiate energy over 360 degrees alonga longitudinal span of about 3 to 5 cm. In yet other body lumens, thespiral window 5899 may radiate energy over 360 degrees along alongitudinal span of about 5 to 7 cm. In yet other body lumens, thespiral window 5899 may radiate energy over 360 degrees along alongitudinal span of over 7 cm.

FIG. 58C illustrates a renal artery RA after the application ofdenervation energy by the device illustrated in FIG. 58A-B. Thedenervation energy applied to the renal artery RA through the windows5899 generates a corresponding denervation zone 5874. The 360 degreeheating pattern is applied across a portion of the renal artery toderivate the kidney without causing morbidity resulting from vessel walldamage. Other treatment angles that may be utilized include 90 degreeheating patterns, 180 degree heating patterns, 180 degree heatingpatterns and 450 degree heating patterns.

A method for using the embodiments described herein includes the stepsof accessing the femoral artery; placing a long sheath for renal arteryaccess into the femoral artery, abdominal aorta and renal artery;placing a flexible microwave catheter 30 according to one embodiment ofthe present disclosure into the long sheath, and into a portion of therenal artery, delivering microwave energy to the anatomical radiatingstructure via a flexible coaxial cable, continuing the energy deliveryuntil a sufficient amount of energy has been delivered to damagetargeted nerve structures while preserving the critical structure of therenal artery by cooling (e.g. by circulation of blood), and removing themicrowave catheter, removing the long sheath, and closing access to thefemoral artery. Another step in the method may include the step ofmonitoring fluid temperature for dangerous temperature elevation via adistally positioned temperature sensor.

Another method for using the embodiments described herein includes thesteps of placing a flexible microwave catheter, including one or moreembodiments described herein, into the renal artery via an intravascularapproach; utilizing a retractable sheath to deploy an electricallyconductive mesh (according to an embodiment described herein) about aradiating portion (e.g., feed gap) wherein the conductive mesh enhancesmicrowave energy delivery to the renal nerves (e.g., sympathetic nervessurrounding the renal artery) by generating an anatomical waveguide thatresonates microwave signals through tissue. Another step in the methodincludes providing a location in the electrically conductive mesh havinga window characterized by the lack of material thereby generating anablation region related to the window. Another step in the method mayinclude providing a fluid cooling structure to enhance energy deliveryand reduce cable heating of tissues surrounding the access path. Anotherstep may include providing a catheter hub that allows for the flexiblecoaxial structure to slide longitudinally therethrough.

The described embodiments of the present disclosure are intended to beillustrative rather than restrictive, and are not intended to representevery embodiment of the present disclosure. Further variations of theabove-disclosed embodiments and other features and functions, oralternatives thereof, may be made or desirably combined into many otherdifferent systems or applications without departing from the spirit orscope of the disclosure as set forth herein and/or in the followingclaims both literally and in equivalents recognized in law.

What is claimed is:
 1. A method for forming a resonating structurewithin a body lumen, the method comprising: advancing a flexiblemicrowave catheter into a body lumen of a patient, the flexiblemicrowave catheter including: a radiating portion at the distal end ofthe flexible microwave catheter, the radiating portion configured toreceive microwave energy, and at least one centering device proximatethe radiating portion configured to deploy radially outward from theflexible microwave catheter; positioning the radiating portion neartargeted tissue; deploying the at least one centering device radiallyoutward from the flexible microwave catheter within the body lumen suchthat a longitudinal axis of the radiating portion is substantiallyparallel with and at a fixed distance from a longitudinal axis of thebody lumen near the targeted tissue; and delivering microwave energy tothe radiating portion such that a circumferentially balanced resonatingstructure is formed with the body lumen.
 2. The method according toclaim 1, wherein the circumferentially balanced resonating structureradiates energy 360 degrees around the longitudinal axis of theradiating portion and along a longitudinal span of about 2 to about 3cm.
 3. The method of claim 1, wherein the body lumen is the renalartery.
 4. The method of claim 3, wherein the targeted tissue is one ormore renal nerves and the circumferentially balanced resonatingstructure generates an electromagnetic field that denervates thetargeted tissue.
 5. The method of claim 1, further including the stepsof: providing a continuous fluid flow within the body lumen; and coolingat least a portion of the body lumen.
 6. The method of claim 5, furtherincluding the steps of: monitoring the temperature of the continuousfluid flow; and terminating the delivery of microwave energy if themonitored temperature exceeds a threshold temperature.
 7. The method ofclaim 1, further including the step of: continuing delivery of themicrowave energy until a sufficient amount of energy is delivered toeffectively damage the targeted tissue while preserving the criticalstructure of the body lumen.
 8. The method of claim 1, wherein the bodylumen is selected from at least one of a gastrointestinal lumen, anauditory lumen, a respiratory system lumen, urinary system lumen, afemale reproductive system lumen, a male reproductive system lumen, avascular system lumen, and an internal organ.
 9. The method of claim 1,further including the step of expanding the body lumen to form astructure related to the microwave frequency.
 10. The method of claim 1,further including the step of delivering microwave energy at a frequencythat is selected to be resonate with the body lumen.
 11. The method ofclaim 1, further including the steps of: monitoring a temperature withinthe body lumen; and terminating the delivery of the microwave energysignal when the temperature exceeds a threshold temperature.
 12. Themethod of claim 1, wherein the radiating portion includes a feed gapforming an open circuit in the flexible microwave catheter.
 13. Themethod of claim 1, wherein the radiating portion includes a first feedgap and a second feed gap, and wherein the first and second feed gapseach form open circuits in the flexible microwave catheter.
 14. A methodfor forming a resonating structure within a body lumen, the methodcomprising: advancing a flexible microwave catheter into a body lumen ofa patient, the flexible microwave catheter including: a radiatingportion at the distal end of the flexible microwave catheter, theradiating portion configured to receive a microwave energy signal at amicrowave frequency; and an electrically conductive mesh adjacent theradiating portion; and a retractable sheath configured to deploy theelectrically conductive mesh about the radiating portion; positioningthe radiating portion adjacent a targeted tissue; retracting theretractable sheath; deploying the electrically conductive mesh radiallyoutward from the flexible microwave catheter and within the body lumenthereby centering the radiating portion at the radial center of the bodylumen; forming a circumferentially balanced resonating structure withinthe body lumen via the radiating portion, and delivering the microwaveenergy signal at the microwave frequency to resonate the body lumen atthe microwave frequency.
 15. The method of claim 14, further includingthe step of: forming a window in the electrically conductive mesh, thewindow being characterized by a lack of material; and heating a regionof the body lumen related to the window.
 16. The method of claim 15,wherein the body lumen is a renal artery, the targeted tissue is a renalnerve, and heating the region of the body lumen related to the window atleast partially denervates the kidney.
 17. The method of claim 16,further including the step of cooling at least a portion of the renalartery.
 18. The method of claim 15, further including the step of:providing a fluid cooling structure to enhance energy delivery andreduce heating of a least a portion of the flexible microwave catheter.19. The method of claim 15, wherein the body lumen is selected from atleast one of a gastrointestinal lumen, an auditory lumen, a respiratorysystem lumen, urinary system lumen, a female reproductive system lumen,a male reproductive system lumen, a vascular system lumen, and aninternal organ.
 20. The method according to claim 15, wherein thecircumferentially balanced resonating structure radiate energy over 360degrees along a longitudinal span of about 2 to 3 cm.